8 MONTHLY WEATHER REVIEW. JANUARY, 1901
~~~ ~ ~__________
possible for a cubic foot of air a t 80° F. to contain 10.93
grains; hence, by dividing the actual amount, 7.99, by the pos-
sible amount 10.93, I obtain for the relative humidity 73 per
cent. On the other hand, suppose that without changing the
actual qmount of vapor in the air I cool down some of the original moist air from SOo F. to 70° F. The above table
shows that at 70° F. our 7.99 grains would be sufficient to saturate a cubh foot of air. Hence the air has now reached
the dew-point, and the moment the temperature falls below
this point condensation of the vapor will begin and will con-
tinue so long as the temperaturwcontinues to fall. When the
temperature has reached GOo F. 2.24 grains of vapor will have
been condensed from each original foot of air.
This condensed vapor will appear either in the form of fog.
snowi rain, or dew, depending upon other conditions. Con-
densation is essentially the rushing together of the surplus
molecules of aqueous vapor, forming small drops of water or
crystals of ice, which become visible as fog or cloud. The
tendency of these minute drops is to fall to the ground, but
the upward air currents are generally quite sufficient to sus-
tain them until the drops grow to a larger size, when they are precipitated as rain. When the condensation is very rapid
the upward curreiits are also rapid and the raindrops are
likely to be large. Of course, snow is formed only when the
temperature of condensation, namely, the dew-poin t, is below
freezing. Precipitation, therefore, depends upon a falling tempera- ture, and the primary question is how may this he brought
about. The most common and effective ways and in the order
of increasing importance are : (1) cooling by contact with
cooler bodies; (2) mixture with air of lower temperature;
(3) loss of heat by radiation; (4) loss of temperature by the
utilization of heat in work. 1. The direct contact of warm, moist air with a cold sur-
face, it doee not matter whether it be a glass containing cold
water or a mountain covered with snow, must result in giving
up heat to the cold object, which thereby becomes warmer.
Now, the quantity of heat that can be taken up by a cold
mountain side is very slight. A little dew may be formed on
the rocks, but this represents the extent of its power to con-
dense moisture out of the air. 2. When equal parts of cold and warm air are mixed
together, both being saturated, a very slight cloud or haze is
formed, due to the fact that the saturated warm air contains
a little more moisture than was necessary to saturate the mixture, but this slight haze is the extent of the precipita-
tion that can be formed in this way.
3. When the air is nearly saturated in the daytime, i t is
apt to cool below its dew-point during the following night-
time; there is thus formed a thin layer of fog near the sur-
face of the earth, or of stratus cloud a few yards above the
surface, or perhaps alto-stratus a few thousand feet above that.
In either case, the lower side of the fog or cloud receives heat
from the earth, while it is only the upper side that cools by
radiation into space. During long nights this cooling may
produce a deep layer of fog, or a thick layer of cloud, and from the upper surface of these there may fall a light, driz-
zling rain ; but this is the maximum extent of the influence
of radiation.
4. The conversion of the molecular energy that we call heat
into the movement of large masses that we call work is the
most important method of cooling. Whenever a given vol-
ume of air flows into a region where the barometric pressure
is less, it expands and in this expansion must push aside the air immediately surrounding it. This is the work that is
done, and i t is exactly equivalent to the amount of heat
energy that is consumed. Thus, the steam in a boiler flows
into the cylinder and pushes the piston ahead, by doing so it
does work and cools off. When the safety valve of the boiler
is open, the steam rushes out with great force, expands greatly
in volume and cools. In fact, i t falls from the temperature
within the boiler to the tomperature of the open air. When
this process takes place quickly and no other heat comes
in to disturb the conditions, this is called adiabatic expan-
sion or adiabatic cooling. Whenever a mass of moist air is
pushed by the wind over a hill or mountain i t expands as i t
asce7de because the pressure diminishes with a1 ti tude, and
its temperature may easily be reduced below the dew-point,
so that by cooling it forms a cloud and by still further cool-
ing may form rain. Ascending air, under the ordinary baro-
metric conditions, must cool at the rate of lo C . for about 100
meters of ascent, or lo F. for 183 feet of ascent. Thus, sup-
pose our cubic foot of air a t SOo F. to be lifted 1830 feet i t
would then have cooled to a temperature of 70° F. a.nd be
saturated : should it be carried still higher condensatiou must
occur. It is evident that the height to which a body of air
must be raised before condensatiou begins depends upon both
the temperature and the humidity of the air at sea level.
Hence in regions of high humidity comparatively low moun-
tains may be important agents in bringing about rainfall, whereas in regions of low humidity very high mountains may
have little influence. There are mountains which rise to such a height that the air about their summits has a tomperature
of freezing or less, 00 that the mountains have a crown of
perpetual snow.
The oflice of mountains is to force the warm moist surface wind into higher regions whereby it is expanded and cooled,
and in this way only do they bring about condensation and
precipitation. A single peak, even if very high, may not be
very effective, as the air currents may pass around i t instead.
of over it, and will merely form clouds in the region of
slightly diminished pressure and upward rising curren ts on
the leeward side of the peak. But in the case of a mountain
range the whole mass of air driven by the wind must pass
over and must, therefore, rise to higher regions in order to do
so. The mistake should not be made of supposing that the mountain “acts as a condenser” in the same seuse that a
blade of grass when chilled by radiation, cools the air i n con-
tact with it and accumulates dew. It is evident that if a
mountain did act in this way the moisture would be deposited
on it in the same manner as dew or frost is deposited on the
grass, or on the cool exterior of a glassful of ice water, and the precipitation would not appear as a cloud or as rain. I n
general, the mountains act merely as obstacles to the currents
of air. A mountain may be very effective in the formation
of clouds without having much influence on the rainfall.
The region or side of the mountain upon which the rain will
fall depends almost entirely on the direction from which the
moist wind comes. In some cases the wind deflected upward
by the mountain may continue rising for a short distance be- yond the mountain, so that the rain may fall to the leeward
rather than on the mountain itself.
--.--
ULIMATE AND CORN.
By E. B. WBEN, U. 8. Weather Bureau.
The weather exerts a tacit, though relentless, tyranny over
the labor and the thought of the agriculturist. The proba-
ble influences of the present and prospective weather upon the
growing crops are seldom absent from his mind. But science
teachee that climate is rhythmic, not capricious. Laplace
has shown that the mean temperatureof the mass of the
earth can not have changed in any appreciable measure dur-
ing the entire period of astronomical calculation and that
while the planetary movements remain as at present no
such change can occur. “Astronomical permanency,” he says,
‘& implies an absolute fixedness of the quantity of heat for
MONTHLY WEATHER REVIEW. 9
the mass of the earth.” And the sun’s heat is the leadinl
element of climate, all other conditions depend in the loiq
run upon that. Hence, the sun’s heat being constant, a1 the changes we observe are periodic as regards the astro
nomical units, the day and the year ; and nonperiodic in a1
other cases, the averages returning always to a line of abso
lute permanency.
Climate is the average of seasonal atmospheric conditions
and as corn is an annual plant, these fluctuating seasona
factors must affect its growth. The crop season is in faci
the climatic unit with respect to this cereal. No season ex. actly repeats itself; there are perturbations within relativel)
narrow limits; the plant strives perpetually to adjust itselj
to perfect correspondence with its environment. As this en- vironment, that is, climate and food supply, vibrates now
one way, now another about a fixed mean, the consequenl
variations of the plant will be compensatory, and so then
should be no final permanent modification of the plant in a
given locality. The tendency in the long run is toward a
more and more perfect correspondence with environment, to.
ward what Spencer calls the one essential to perfect life.
That the study of climate, as well as soil, in all its bear- ings upon the great American staple is as profitable as any
that engages the attention of the Government is shown by
the results already attained, but still more by certain eco.
nomic considerations. It is a surprising, even startling, fact that the average yield of corn in the United States is only
about twenty-three buehels per acre, while a prize yield of
more than two hundred bushels is well authenticated. The world is just beginning to appreciate the value of corn as a
food, and in the new commercial era that is dawning upon
our country it will devolve upon us to supply a large part of
the world’s demand for this cereal. No valid reason is ap- phrent why the average annual yield should not be twice or
thrice what it now is. Aside from its direct control of the amount and quality of
the crop, climatic variations, by vitiating experience, impede
agricultural progress. This fact is most apparent in the agricultural history of a new country, where experience ac-
quired in one section is in many cases not only useless, but
positively pernicious when applied to a distant section. In the United States millions of dollars have been loet through
the efforts of new settlere to learn by experience the climatic
peculiarities of their adopted home. It is the province of
agricultural science to teach us how to profit by the experi- ence that has been 80 dearly bought in the past.
Agricultural climatology considers the relations between
the meteorological elements measured in terms of plant devel-
opment. As intimate as these relations are known to be, and
an interesting and promising a field as their study is known
to offer, it is rather surprising that no adequate organized
effort has yet been expended in this direction. But we are coming to see that the very fact of this intimate reciprocal
dependence may be turned to advantage, and that by methods
of correlation the facts of each science may be made to illu-
mine the other.
The laws of biological and of meteorological phenomena
separately considered are extremely subtle and complex, and
any attempt to study them in their manifold reciprocal rela-
tions is sufficiently difficult to deter any but the best equipped
and most zealous students. This difficulty of properly inter- preting the separate effects upon vegetation of heat, light,
moisture, and the gases of the atmosphere is enhanced by the
fact that a change in one meteorological condition ordinarily
disturbs all the other elements. For example, rain is accom- panied by cloudiness, decrease in light and heat, and, it may
be, by an increase of warmth in the soil, if the rain be a warm one.
Extended and elaborate; meteorological - observations have
-2
been conducted in this country and in Europe, but instru- ments measure only detached elements of climate ; plants
alone record its composite or cumulative effects. Hence, the insistence on the part of leading agricultural scientists that
climate should be studied in terms of plant life. Such study is termed phenology, and while it has led to some valuable
generalizations, the fragmentary character of the data viti-
ate@ many of ite conclusions. It appears that in the past phenologists have given the element of heat undue, if not
almost exclusive, weight. It is becoming more and more
evident that the real function and value of light have been
neglected and undervalued. A fundamental theory which has been held by botanists for more than a century is, briefly,
that a certain life event takes place in any species whenever
that species has been exposed to a certain sum total of heat,
which is called the physiological constant or thermal con-
stant. In harmony with this theory, Blodgett, in his Clima- tology of the United States, says with regard to corn that its
period of growth is precisely proportional to the abruptness
of the temperature curve ; that its unusual elasticity of con- stitution admits it to all regions where the temperature
reaches a certain point, however brief the duration of this
warm period may be. He defines the extreme northern limits
of Indian corn as coincident with the isotherm of 670 for
July, though a somewhat higher mean for one summer month
is required, and he attributes the increase of productiveness at the north mainly to &‘the hasty growth, the excess of heat
while it lasts, and the hastened ripening period.” The seem-
ingly insignificant item of a deficiency of two degrees on the
mean of a single summer month practically excludes thie
crop from the British Isles, where it is grown, when grown
a t all, only as a forage crop, seldom maturing any grain.
This statement of the subject bas been for fifty years the
popular and the current theory. Temperature being the most
easily measured of the solar manifestations, it has quite
naturally been regarded as the dominant one. Then, too, the
rudimentary state of climatology made necessary such a sim-
plification as is afforded by the consideration of heat alone. The trend of recent opinion is summarized by Professor
Abbe in his extensive manuscript report of June, 1891, on the Relations of Climate and Crops, where, after reviewing the investigations of Tisserand, he concludes :
That the temperature of the air has apparently little to do, in and of ,&self, with the duration of time from sowing to ripening, but that this lepends principally on the sunshine. The temperature of the air con- role the chemical composition of the seed, but the effective sunshine seems to be the productive climatic element; it furnishes the total mergy at the disposal of the plant, but it is also the one least etudied md understood.
Professor Sturtevant, of New I‘ork, from tests with 128
varieties, concludes that “ actinism has an influence scarcely gecondary to temperature.”
So it would seem wise in the light of recent study to attrib-
lite much of the hostility of a climate like that of England
to the greater degree of cloudiness, and the congeniality of
the climate of our western States to the habitually clear skies
If summer.
In discussing climate and corn it will be convenient to
treat their relations first historically and then analytically ;
z cursory glance at the more evident accumulated results of
:limetic modification and limitation will prepare the way for
tn outline of the individual factors that constitute environ-
nent and the principles that govern the life of the plant.
The original home of corn, or maize, is now quite certainly
mown to have been in central Mexico, and hence it is the
mly one of our cereale that is indigenous to the New World.
[t has been so long and so thoroughly domesticated that no truly wild varieties are known. I n geographical range and
dasticity of habit it probably surpasses every other cultivated
plant. From its original tropical home it has spread to the
10 MONTHLY WEATHER REVIEW. JANUARY, 1901
temperate as well as the tropical regions of the world. Intro-
duced into Europe soon after the conquest of Mexico, i t finds
a genial home only in the warm valleys of the south and cen-
tral portions of that continent; i t is extensively grown in
Africa, and in India it thrives everywhere throughout the hill country; it appears to flourish as well in the temperate
as the tropical regions, and at altitudes of from sea level to
7,000 feet or more.
Corn is, however, as it has always been and will undoubtedly remain, a distinctive and characteristic American product.
It is cultivated from Canada to Patagonia, over 7,000 miles
of latitude. It has been known to ripen as far north as 63O and has been found a profitable crop in latitude 51° north.
I n response to the multifarious conditioiis which this great
range imposes, Colin tless varieties have been developed, there being over 200 in the United States alone. It is interesting to coneider some of the extremes of variation as exhibited by
the plant and the ear, variations that have their origin ulti-
mately in climate and acclimatization. The niatured plant
ranges from 2 to 23 feet in height; stalke as tall as 30 feet
have been found in the West Indies, and a nornial plant 18
inches in height has been known to mature perfect ears.
Ears have been known as small as 14 inches and as great as
16 inches in length. The number of rows of grains to the
ear ranges from 6 to 40 or more. The period for growth and
maturity varies from six weeks to seten nionths. Besides the usual colors, white, yellow, and red, the grain is also found to
be violet! purple, blue, slate, black, and variegated. Inci- dentally it may be said that color is by some considered the
most stable feature, and red corn is believed to possess a
greater fixity of type than any other. Along with these re- markable extremes in size, a corresponding range of total
yield is found ; though the total crop does not, of course, de-
pend directly upon the size of the ears or of the kernels.
Nevertheless there is a very wide disparity in productiveness
depending upon climatic irregularities independent of soil
fertility or of food supply. Both in quality and prodnctive- ness corn has improved to a marked degree in the higher
latitudes to which i t has spread. Indeed, i t is a rather strik- ing fact that the maximuni yield is found near the northern
limit of its cultivation. The weight of the grain per bushel
is also usually greater a t the north. Corn thus presents a rather unique instance of a plant which by culture and ac-
climatization has come to thrive hetter in an alien home.
This result will be seen later to depend upoii a general law.
In no other section of the world, however, does the yield of
corn in any way equal that of the corn belt of the United
Btates, or the seven corn surplus States from Ohio to Nebraska
and Kansas, inclusive. To be sure corn is grown, and one or more of its many varieties may thrive, in every State and
Territory of the Union, yet in 1899 six States raised nearly
60 per cent of the crop, and twenty-five States now produce
95 per cent of the total yield. As an illustration of the great acreage devoted to corn, it has been said that the eleven cotton
States as a whole give a greater area to corn than to cotton.
The better adaptability of the high temperate regions to
corn is not altogether an unmitigated advantage. In the United States the seasonal limits preclude the possibility of
more than one crop a year, though in southern California, with the aid of irrigation, two crops in one year have been
raised, arid in most tropical regions two and sometimes three
crops a year are regularly grown on the same ground. Not only does the change in latit,ude modify, but transportation
in longitude produces effects almost as notable. According to Darwin, American white dent corn cultivated in Germany for three years without selection was greatly reduced in size,
lost its dented character, and assumed a yellow color common
to corn in that country. Changes almost as marked have
occurred in a few generatione in corn from one part of the
United States when removed to a distant part. According to
Professor Beal a soft gourd corn from Texas, after cultivation
in Louisiana for twelve years, became a hard flint with larger
cob. An 8-rowed flint corn from the north, after seven years’ cul tivation without selection in Ohio, became much dented
and the number of rows increased from 12 to 20.
The ratio of weight or size of total plant to grain varies
according to somewhat definite laws. In the United States
there is, generally speaking, a uniform decrease in the height
of the plant from 12 feet in the Gulf States to 6 feet in Canada.
Accompanying this dwarfing of the plant by the progressive
increase of cold, there is, up to a certain latitude, an almost
equal increase of grain. Hence, there would seem to exist
for any given variety a certain fixed optimum ratio between
plant and grain ; this ratio has not been determined, how-
ever, and seems to have received but little attention. Another
concomitant, or it may be result of this dwarfing by cold, is a prominent tendency of the dwarfed varieties to develop
suckers. This tendency may also appear locally whenever
the growth of the stern is retarded, and is probably due to
sustained activity of the roots and the subterranean portions
of the stem, which retaining the higher temperature of the
soil, promote the development of new stems. DwarBng at
the north is further accompanied by a shortening of the iuternodes of the stem and an increased leaf surface. This
increase of foliage in high latitudes is undoubtedly due, in
large part, to the necessity for more rapid assimilation in the shorter season, the special function of the leaf being, as we
shall see, to absorb the energy of the sun’s light and to con- trol, by means of respiration, the food supply and the water
content of the plant. Regarding the differences in composi-
tion of the grain but little of a conclusive nature is estab-
lished; as with many other changes this is masked by changes in the food supply depending on the chemical activi-
ties of the soil, which activities depend in turn upon the
climate. From an economic basis, perhaps the most con-
spicuous and certainly the most valuable feature of the corn
plant is its elasticity with respect to the length of the
period of growth: the varieties cultivated in the United States require a t the south from one hundred to oiie hundred and
seventy days for the best yield, while Blodgett mentions, in
the valley of the Red River of the North, varieties that ma- ture in sixty days.
Turning now to an analytical survey of the separate fac-
tors that constitute climate and their individual effects on
the plant and on seed, brevity demands that all reference to methods and experiments be omitted and that only conclu-
sions be stated. Introductory to this survey there will be
given a review of the relations of the plant to its environ-
ment in general, and then of the means and methods of its
response and adjustment to this environment, or what is
termed the physiology of the plant. All that can be under-
taken here is a compilation and a classi6cation of results,
and while the general subject is the relation of climate and
corn, many of the statements that follow are generalizations
that apply as aptly to other crops. I n view of the difficulty
of separating the individual from the combined effects of the
meteorological elements, and tbe paucity of reliable data,
this treatment will necessarily be fragmentary. The effects of climate on corn may be appropriately classi-
fied as immediate, intermediate, and incidental.
Professor Storer has tersely and beautifully said that the
prime object of agriculture is to collect for purposes of hu-
man aggrandizement as much as may be poesible of the
energy that comes from the sun in the form of light and
heat. Now the working capacity of sunshine is, according
to Kelvin, one-horse power for every 7 square feet of surface.
Measured by the standards of mechanics, how inefficient and
wasteful an engine is our agriculture a t its best. The atmos-
JANUARY, 1901. MONTHLY WkATHBR REVIEW. 11
phere is directly the source of 96 per cent of the material i n
the total plant and of 98 per cent of the matter in the grai
of corn. The plant is an elaborate machine that absorb
and transforms energy, utilizing solar radiation to diges
carbon dioxide in the leaves and to combine into vegetabl
organs and tissues the gases of the air with the elements sup
plied by the soil. When we remember that the amount o
energy available, the food supply, and, consequently, th
amount of matter stored, all depend directly upon meteor
ological conditions, we realize how overwhelming is thl influence of climate.
A grain of corn once matured is as inert as a pebble unti
heat and moisture are applied ; then a sprout and a root ap
pear, each for a separate function, the one for ahsorbin(
etherial waves, the other for absorbing water. I n addition tc heat and moisture, oxygen is absolutely essential to germi
nation, as well as to all subsequent growth. The importancc of moisture will be appreciated when we recall that wate.
performs a t least four distinct offices: first, directly as I
food, being united in the leaves with carbon to form thc
carbohydrates; second, as a solvent for the nutritive mat ters in the soil ; third, as the vehicle which transports thc
soluble food through the roots and stems to the leaves ; and
finally, ae a cooling device, since, through evaporation, watei
largely controls the temperature of the plant. The “frec
water of vegetation,” as it is called, or the water of the juices
comprises from 70 to 90 per cent of corn in the fodder stage
while the “combined water of vegetation,” or the water thai
remains after the plant is air-dried, is 12 per cent in a kerne:
of corn.
The immediate effects of climate will be better understood
by glancing first at its intermediate effects through the me.
dium of the soil and. through the food suppy. Climate
originates soil and all the capacities of the earth for tillage
and i t is a t the same time more than soil or tillage. For in a
truly “good year” the worst tilled soil returns a more boun-
tiful harvest than it is possible with all our industry to ex.
tort from the best tilled soil in a “bad year.” The oasif
differs from the desert only in the item of water supply, and
a given climate does not result primarily from the nature of
the earth’s surface; on the contrary, that surface is deter.
mined almost wholly by climate. The agencies that produce,
and are producing arable areas from the seemingly imper-
vious and indurate rocks, must continue their action peren-
nially if the soil is to maintain itself. Indeed, the reverse
metamorphosis is constantly a t work. The greater part of
the known rock formations were once in the form of soil,
and chemical, physical, and even vital forces are continually
engaged in the work of rock making, as well as rock breaking,
so that an important office of agriculture is to oppose this
cyclic law of nature, and to counteract the retrogressive ten-
dency from soil to rock.
Primarily, the soil is a reservoir of moisture and plant
food; but hardly secondary is its ofice as a vast laboratory, wherein during the warmer seasons, countless complex chemi-
cal agencies and numberless microscopic organisms operate
unceaeingly. Indeed, the relations of climate to the plant
through the medium of the soil are so intimate and vital that no just idea of their importance can be given here.
These relations may be classed as physical, chemical, and
biological.
The physical texture of the soil determines its conductivity
for heat and its content of water and air, both of which in
proper proportions are essential to the chemical and biological
functions. Moreover, the water content, through its power
‘to absorb, transform, and conserve radiant energy, coli trols
the temperature of the soil. Finally, soil temperature is
far more effective than the temperature of the air. Heat is well known to accelerate diffusion, solution, osmotic action,
and evaporation. Now these physical proceases are precisely
those that perform the chief, almost the entire work involved
in plant nutrition and growth. Hence, a high soil tempera- ture is essential not oiily for the life of the plant itself but
also for the ventilation and the life of the soil, a healthy
soil being very appropriately called a living mass. On an average, 40 per cent of the radiant energy incident on the soil
is absorbed, conducted downward, and stored in the form of
heat, 60 per cent being lost to the soil by reflection, radia-
tion, and evaporation. The more water a given volume of
soil contains at a given temperature the greater its latent
heat. If the sun impart equal quantities of heat to equal
volumes of sand, clay, humus, and water, then for each degree of rise in temperature of the water the humus will rise over
2O, the clay about 4 O , the sand about 5O. Thus, on account of the high specific heat of water, with a normal amount of
water in the soil, the effect is to retard the warming of the
soil in the spring; but when a wet soil is once heated i t is,
of course, a great reservoir of energy. Again, by virtue of this property of high specific heat, water in the form of warm
rain is a very fertile source of heat for the use of the crop. On the other hand, cold rains and the melting suows of spring
are equally pernicious from this point of view. The work of evaporation in maintaining the ground at a moderate tem-
perature under the fierce sun of summer is evident from the
consideration that the evaporation of 1 pound of water from
1 cubic foot of soil will reduce the mean temperature of that
Boil hy about loo. Actual measurements confirm this theo-
retical conclusion by showing that during the Bummer months
the average temperature of the 3 inches of soil nearest the sur-
face is as much as 1 4 O lower than that of the air. This dif- ference between the temperature of a moist soil and the air
above i t is augmented by any condition that increases evapo-
ration ; consequently it increases with the increase of wind
velocity. Because of this cooling effect of evaporation, too, wet soils are usually cold soiIs, for loss of heat by evaporation
more than counterbalaiices the gain in heat absorbed by the
ioil water, so that the best percentage of water is the least
niiount that will just float the solid food and maintain the ?lants in a healthy state of turgescence.
Oxygen is as indispensable to the chemical life of the soil
ts it is to animal life. Both oxygen and nitrogen are essen-
;ial to the biological processes, and both the chemical and
iiological activities in the soil are as indispensable to the :rop as are sunshine and showers.
The importance of right proportions of water and air in
,he soil is further shown by the fact that the process of decay,
whereby organic material is turned into humus and made
ivailable to the plaut can not go on without an abul;dant
iupply of oxygen. A soil that coutaiiis too much water con-
,aim too little air. The ferments thrive best at a tempera-
m e of 85O to 95O, and when the soil contains from one-half
,o one-third the amount of water required for saturation.
rhe ultimate source of the nitrogen found in vegetable mat-
,er is the air, and plants are unable directly to utilize it in a
‘ree state. The bacteria, which are chiefly concerned in main-
,aining the available supply of nitrogen in the soil, are able
,o work only during the warm seasons, and their activity de-
)ends directly on the temperature of the soil, being a maxi-
num a t 98O. On the other hand, light is inimical to the life
md activity of these soil bacteria, a fact that may have some
learing on the rapid growth of corn during hot nights, inas-
nuch as the work of the microorganisms in feeding the roots
a then facilitated. That corn germinates best a t the high
emperature of 9So to 100° is, undoubtedly, due to its tropical
migin. For Professor Davenport shows that the attunenieu t
If plants to environment as regards temperature has its ori-
;in, not in processes of selection, but in the modifications of
motoplasm by temperature itself.
12 MONTHLY WEATHER REVIEW. JANUARY, 1901
Granted that the soil is porous enough and dry enough to
admit the air readily, ventilation is facilitated by the une-
qual heating of night and day, and by nonperiodic tempera-
ture changes as well. As the air within the soil is heated i t
expands, and some of it is forced downward to the deeper
layers; when it cools it contracts, and free air is drawn into
the soil. The same effect is produced by barometric changes ;
the passage of areas of high and low pressure has been found
to influence the flow of water from drains to the extent of 15
per cent, thus showing an unexpected movement of air in the
soil. The corn belt lies entirely within the region of maxinium
frequenoy and intensity of barometric oscillations in the
United States. Strong, and particularly gusty winds, by a
measurable aspiratory action, have also a significant influence
on Roil breathing.
Climate, as has been said, is typified by the average meteoro-
logical conditions of a season; but these are all more or
less periodic if not erratic. The best crops demand a per-
manence of certain conditions during a certain stage of
growth ; thus, for example, permanency of the moisture is
called for, while rains supply it intermittently. Again, the root hairs developed in a dry soil seem unable to thrive i u a
wet one, and new rootlets must be thrown out to meet the new
conditions. The same is true of rootlets .developed in a wet
soil ; so that, in a soil whose moisture content fluctuates rap-
idly within a wide range, the plant is constantly taxed to
maintain itself.
A regular supply of warmth is more genial than sudden
transitions from heat to cold. Knowing these things it is the
part of husbandry to ameliorate the eccentricities of the cli-
mate in order to improve the crop.
The effects of climate on the crop through the medium of
the soil are classed as intermediate; but it will be seen that
eome of these effects are as truly direct as are the effects of
sunlight and the temperature of the air.
Having seen how heat, light, moisture, and the supply of
gases operate to control the supply of those ingredients that
are furnished by the soil and that constitute in the main the
ash of the plant, we return now to the immediate effect of
these elements on the vital processes and assimilation. The elaboration of the various elements that are fonnd in
a normal corn plant, of which there are about 14, takes place exclusively in the presence of the chlorophyl, or green matter
of the leaves and stems, and only under the energy of sun-
light. Heat alone is powerless to begin or to carry on this
work, yet a relatively high temperature is nevertheless
essen tial.
I n the presence of sunlight the leaf pores, or stomata, open
wide to admit a freer circulation of air in the blades. Of
, these pores there are in the blade of corn about sixty thousand to the square inch on the upper surface and ninety thousand
on the under surface; their dilation and contraction and con-
sequent control over ventilation and respiration is propor-
tional to the intensity of sunlight, and hence very intense
sunlight may of itself cause wilting independently of its
heating effects. The orange and yellow rays are the most active in the work
of decomposing carbon dioxide ; the relative energy of the
different colors for this purpose correspond closely with their relative brightness.
While light is indispensable to the assimilation of carbon
dioxide, it undoubtedly exerts a directly retarding influence
on growth proper, or cell multiplication, but the beneficial
effects of the higher temperature that accompanies daylight
more than counteract this. The blue rays, opposing certain chemical changes, are those most effective in retarding growth. Sachs showed that for many plants when kept a t a uniform
temperature the rate of growth gradually increases during the
night and is.a maximum shortly after daybreak. This effect
of light is opposed to the effect of the diprnal temperature ;
heat and light increase transpiration, which means a loss of
water, and hence less growth. This aensitiveness and response
of protoplasm to light is the result of the chemical changes
wrought therein by the light.
By osmotic action the root hairs imbibe the liquid food that
surrounds them ; capillary and osmotic actions carry this
supply to every part of the plant, to the tip of every blade,
which is not only bathed in air, but has its microscopic in-
terstices permeated with it. Here, in the leaf cells, the carbon
dioxide of the air, which is practically an invariable quantity,
conies in contact with the water that has been brought from
the roots. Here, too, the energy of the ether waves, which we call light, but which the vegetable cell recognizes only as
force, or a mode of motion, causes the carbon dioxide to part
with some of its oxygen in exchange for some of the hydrogen
contained in the water. Thus, there is formed within the cell
a substance composed of carbon, hydrogen, and oxygen, the
exact molecular structure of which is not known; in this
process some of the oxygen is freed and thrown off by trans-
piration. By the introduction of the molecule of carbon dioxide into the cell the equilibrium in the atmosphere of
that gas is disturbed and another molecule diffuses into its
place; for this gas exists and behaves as if i t were the only
gas present in the space under consideration, the same law
being true for each of the gaseous elements whose mixture
constitutes what is called the atmosphere. The consumption
of carbon dioxide tends constantly to produce a vacuum in
the carbon dioxide atmosphere, and the law of diffusion as
constantly tends to maintain the supply. If molecules of
hydrogen are withdrawn from the fluid contents of the cell, in-
stantly osmosis and diffusion tend to replace them; the same
is true of the solid particles in solution. Assimilation within
the cells of the leaves perpetually destroys the equilibrium of
osmotic pressure, hence this pressure creates a constant flow
toward the seat of demand. Evaporation from the leaves, which is proportional to temperature and is accelerated by
winds, as is the supply of carbon dioxide, operates in the same
direction, viz, to destroy the equilibrium in the leaf cells and
channels, and consequently the tiny streams from the root- lets are hastened onward with their precious stores of food.
Cold not only stiffens the sap and retards its flow, but also
slackens molecular motion and hinders the chemical reorgan-
ization of the elements. The process of evaporation proper
is, however, almost independent of the processes of nutrition,
and is rather a L L necessary evil.” The most rapid growth fre-
quently occurs under precisely those conditions that make evaporation least rapid.
The quantity of water that passes through the plant and
is transpired and evaporated is enormous. The average ie
about three hundred parts of water to one of dry matter.
According to experiments by Professor King of the Wiscon-
sin Experiment Station, dent corn used three hundred and
ten tons, and flint corn two hundred and thirty-four tons of
water for each ton of dry matter produced. This same ex-
perimenter supplied growing corn with water as fast as it could be used to advantage, and found that the crop con-
sumed during its ieason of growth water equivalent to a rain-
fall of 34.3 inches, and yielded more than four timesas
bountifully as a very large crop grown under the best natural
conditione of rainfall in Wisconsin. And he concludes that “large as this movement of water is, i t is seldom great
enough to enable a moderately fertile field to produce its
largest crops.” And these tests in Wisconsin merely confirm
a conclusion that is becoming quite general, and is prompt-
ing the advocacy of irrigation even in the humid regione.
Moreover, the quantity of water producing a given rebult in-
creases with the fertility of the soil, and, according to Wollny,
the soil moisture produces its maximum results only when
JANUARY, 1901. MONTHLY WEATHER REVIEW. 13
the plants are grown in the strongest light. The value of a
given quantity of rainfall for the crop increases as the num- ber of rains, and what has been called the useful remainder
of rainfall is only 20 per cent of the total amount, percola-
tion and evaporation accounting for 80 per cent. Percolation
is a fertile source of loss of the valuable soil nitrates, especi-
ally in the wet fall and winter seasons, when the corn field
is bare and a large proportion of the water escapes down- ward. Rain, like snow, is the “ poor mau’s fertilizer,” bring-
ing down, per acre, in the course of a year, a t Rothamsted, England, 24 pounds of salt, 44 pounds of nitrogen, 18 pounds
of sulphuric acid, and much carbon dioxide, which is a valu-
ble solvent. A single drought late in July or August, during the critical period of tasselling or earing, has cost the West-
ern States 1OO,OOO,OOO bushels of corn. A wet harvest time
results often in a dilute sap, and, consequently, a soft grain,
which is the prey of microbes and fungi fhat thrive in damp-
ness. These miscellaneous considerations show that in many
unsuspected directions the question of moisture is a vital
one, and that to husband it is the first duty of the farmer.
Some of the less important incidental relations of climate
and corn, such as electricity, winds, frost, iusect enemies, and
diseases remain to be mentioned. Electricity artificially ap-
plied to the roots by charging the soil, and to the leaves by
means of the electric light, have both repeatedly been foiind
to stimulate the growth, and in some instances, greatly to
accelerate it. Recent experiments show that when green
leaves are exposed to direct sunlight there is developed a dif-
ference of electrical potential between the illumined and the
shaded surfaces, amounting in some cases to .02 volt, but the
bearing of this fact upon assimilation is not well known.
Atmospheric electricity is a fertile source of ozone, or con-
densed oxygen, which is particularly active in the production
of nitric acid. Electricity stimulates protoplasm, the ulti-
mate vital principle, and may determine the character of its
activities, but under natural conditions this element is be-
lieved to have but slight influence.
Winds have been called the vehicle of climate ; but we are
concerned here with their incidental and accidental features
only. In the semi-arid regions broad, unprotected fields are
frequently swept by high winds that remove two or three inches of the light surface soil, and with it the seed of the
young crop. Strong winds during the period of maturity of
the corn crop, especially after the roots have lost their vigor,
by “lodging” the corn and subjecting i t to the dangers of
decay on the wet ground are often the occasion of great in-
convenience, if not of serious damage. But the most remarli-
able immediate phases of this meteorological element are the
hot winds that frequently ravage the corn belt west of the
ninety-fifth meridian from Dakota to Texas. In 1888 ten
Kansas counties reported an estimated loss of 21,000,000
bushels from this cause. These devastating blasts (fed by
descending currents of air so hot and so dry as to abstract
moisture faster than transpiration can supply it, and hence
literally to burn the plants) are perpetuated by conditioue
of drought, and are most fatal during the critical stages of
tasseling and earing. The moisture content of the soil and the nature of the winds have intimate reciprocal relations,
and truly dessicating winds are improbable for auy protracted
period over a well-watered region.
Because it possesses such exceptional recuperative powers
as to make it almost invulnerable to the hot winds of the
semiarid weet, it is worth while in this connection to men-
tion kaffir corn, which the Department of Agriculture intro-
duced in the early eighties from Africa, where i t attracted
attention on account of its peculiar drought resisting property,
due largely to the fact that its roots penetrate to the depth of 18 or 20 inches.
While light frosts in autumn (by hastening maturity in a
dangerous time) often prove wholesome, an4 while the value
of thtj frosts of winter in disintegrating and preparing the
soil for the subsequeut crop is so well known as to require
only a passing mention, on the whole the range of corn is
much restricted and the crop imperiled by this element.
Experts of the Department of Agriculture assure me that
they regard it as quite probable that a kind of corn may
ultimately be developed which will possess immunity from
frost; but as yet the average interval between spring and
autumn frosts virtually limits the growing season. The
character of a winter may also affect the vigor aud germi- nating power of the graiu that is stored a0 seed for the
subsequent crop. Seasonal characteristics have practical connection, too, with
the insect pests and diseases of corn. Not only during the
crop season are these pests largely at the mercy of the ele-
ments, but fitful winters are sure to prove destructive to them,
for during the bright, warm days eggs are hatched, chrysa-
lides matured, and insects lured from their retreats, only
to be caught and destroyed by the sudden cold waves. The
fungus diseases, such as rust and smut, are carried by winds and are favored by wet seasons, dews, and moist atmosphere.
Many important facts bearing directly on the subject of
this paper are found in the extensive report of 1891, above
alluded to, by Professor Abbe, on the Relations of Climate to
Crops. They will here be summarized, and while these deduc-
tions apply with equal weight to all annual crops, their im-
portance is especially patent in the case of a crop with so
extensive a range as corn.
Growing out of the interrelations of climates and plants
there are two laws that admit of tolerably definite statement.
These are the law of habit and the law of economy. Where-
ever the supply of heat is always sufficient the variations of
moisture control, and wherever the supply of moisture is al-
ways sufficient the periodicity of heat controls the whole de-
velopment of the plant. In other words, if the periodicity
of heat is such as to warn of the necessity of economy, the
whole life of the plant is determined by the course of heat,
and the same for moisture. On the plains of South America,
for instance, the dry season exerts the same influence as our northern winters. In the Middle States. not the rainfall of spring so much as what seems an instinctive knowledge of the
approaching drought, stimulates the corn to a hasty develop-
ment; a t the north the growth is correspondingly accelerated
by the knowledge of the rapidly approaching frosts of au-
tumn. So sensitive ie the plant to the changes of climate
that even the ordinary seasonal irregularities have a strong
influence; the general disposition acquired by the seed in a
single dry or wet, wmm or cold, early or late, season prepares
it by virtue of that experience to become the best seed for
planting in anticipation of another such season as that in
which the seed was matured. This tendency is illustrated by
the well-known fact that dwarfed varieties of corn from north-
ern latitudes, when cultivated to the southward, mature
earlier, are hardier, and more prolific than the native varie-
ties. A corollary of great practical promise is that in a re-
gion habitually or frequently dry, corn raised in the driest
years should be preserved for seed, as likely to be far better
than any that may be brought from a distance. Hence the
common, if not universal, practice of using seed grown in the preceding year is strongly condemned. By always utilizing
seed that has been raised in the driest years one may hope
speedily to develop varieties whose vegetating period will be
so short that the crop will rarely be injured by the hot winds of July or August. And a similar rule would apply for any
desired disposition we may seek to impress upon the seed.
In the light of these facts it is suggested that irrigation
may come to be used as a temporary device to promote the
evolution of new vmieties that can be cultivated without irri-
14 MONTHLY WEATHER REVIEW. JANUARY, 1901
gation. On the other hand, recent careful work in France
has demonstrated that when the plants are forced to their
maximum yield by irrigation the seed thereby suffers a
marked deterioration, and that for continued maximum re-
sults the seed must be raised on dry soil.
Climate being inviolable and inexorable, what hope is there
that the agriculturist shall be emancipated from the tyranny
of frost and drought? Clearly, he must attain this by work
on the soil and 011 the plant.
By utilizing vast stores of energyin the form of fuel man
banishes the rigoreof winter, thus creatingartificial conditione
of shelter and heat, by aid of which he has supplemented
the process of acclimatization. Thus, also, must he cooperate
with nature in behalf of the plant; he must combat her
malignant aspects by intelligent selection ; by scientific meth-
ods of culture he must supplement her beneficent efforts on
behalf of the human race.
METBODS EMPLOYED IN THE DISTRIBUTION OF
WEATHER FORECASTS.
By JAMES BERRY. Chief of Cllmate and Crop Division.
After making the most accurate prognostications practicable
the Weather Bureau has 110 more important duty than to
give them the most extended publicity that its facilities
afford . As with other classes of information the newspapere are
the media for most effective work, and as every important
Dewspaper in the country gives prominent place to the
weather forecast, a dieseniiuation is obtained so extensive as
to be almost incalculable. The cities, towns, and thickly
populated communities, through the newspapers have, there-
fore, not suffered for lack of weather information, hut the
rural districts have been less fortunate, and the devising of
plaus by which the agricultural classes might receive the
forecasts in time to guide them in their daily avocations has
been a difficult problem. The Bureau since its establishment has from time to time
considered many methods by which the forecasts might be
made to reach the agricultural classes in time to be of use,
and aside from the eEorts of its officials, suggestions from
others interested in the subject have been nunierous. A vast
majority of the latter, however, from one cause or another,
have been impracticable, so that after the thirty years of ex- perience the Bureau accomplishes its distribution of forecasts
and special warnings priucipally through ( 1) the newspa-
pers; (2) the system of telegraphic di~trihution, a t Govern-
mciit vxpense, under direct supervision of Weather Bureau
statiou officials ; (3) the voluntary cooperation of railroad and
telephone companies, public spirited citizens, and postmasters.
The organization of the local State Weather Services dur-
ing the eighties tended to augment the interest taken in this
subject and resulted in the adoption of the systems that now
give to nearly every part of the country having mail or tele-
graph facilities, daily forecasts and warnings of unusual
weather conditions.
The country has been divided into districts with a center
of distribution for each, from which the forecasts are tele-
graphed daily, except Sundays and holidays, to subcenters
for redistribution by telephone, mail, or railway bulletin
service. The distributing points receive predictions by tele-
graph or telephone usually by 10:30 or 11 a. m., seventy-fifth
meridian time, and the substations served by mail get theirs
within a few hours thereafter, depending upon distance and mail connections.
Independent of the distribution attained through the press,
there are now published daily more than 100,000 weather
bulletins, much the greater part being in the form of postal
cards printed from the telegraphic report received by post-
masters at distributing points and sent to the outlying towns for display in suitable holders in post o%ices and other promi-
nent places. Postmasters at distributing offices are largely
relied upon in making this distribution. By a simple print-
ing device the franked cards are rapidly printed in bold type,
and the earliest mails carry them quickly to their destination.
Logotypes are used, comprising a vocabulary of about 125 of
the popular weather terms in which the weather forecasts
are usually expressed. The forecast cards are stamped in a
very expeditious manner, it being possible for one person to
print several hundred cards within a few minutes. In the
whole experience of the Weather Bureau no system has been
tried that has proved more effective or inexpensive than this
extremely siniple method of stamping the forecaste by hand
ou postal cards bearing the official frank.
Other and older systems for conveying weather information
have not been abandoned, viz, the flag displays and sound
signals. The former consists of a series of five flags, which
are displayed singly or in such combinations as to represent
weather conditions. The sound signals are a code of steam
whistle blasts which may be heard for miles in the country
adjacent to the mill or factory sotinding the same. This eys-
tern is quite extensively used in some States, and has proved
very popular. The code employed is the following:
A warning hlast uf from fifteen to twenty seconds duration is sounded to attract attention. After this warning the longer blasts (of from four to six seconds duration) refer to weather, anal shorter blasts (of from one to three seconds duration) refer to temperature; those for weather are sounded first.
Blasts. Indicate.
TWO long.. ................... .Rain or snow. One long.. .................... .Fair weather.
Three long.. ................. .Local rain or snow. One short .................... .Lower temperature.
rhree short ................... Colt1 wave.
Two short.. ................... .Higher temperature.
By repeating each combinntion a few times, with intervals of ten seconds, liability to error in reading the signals may be avoided.
ESPLANATION OF \\'EATHER FLAGS.
No. 1. NO. 2. No. 8. No. 4. No. 5.
White Flag. Blue Flap. White and Black Trl- White Flag Blue F l a g . angularFlag. with black square in center.
Cl& or fair Rain or Snow. Local Rain or Temperature. Cold Wave.
When number 4 is placed above number I , 2, or 3, it indicates warmer; when below, colder: when not displayed, the temperature is expected to remain about stationar . During the late spring and early fall the cold wave flag is also useito indicate anticipated frosts.
Quite a variety of methods other than the aforementioned
have been tried from time to time, some giving much satis-
faction, among which may be mentioned the plan of attach-
ing to letter boxes a suitable frame, the card forecasts being
placed therein by the letter carriers in making their rounds
for the collection of mail. This system is in vogue in several
cities and is very popular. The street cars are also used to a
considerable extent, the forecasts being posted in the interior
of the cars in bulletiu form, and in some iustaiices symbols
representing the flags are displayed from the sides or tops of
the cars. Within the year 1900 there has been utilized what now prom-
ises to be one of the most efiective methods of reaching the
agriciil tural classes, viz, the rural free mail service. Wherever
it has been possible to reach the distributing post ofice with the telegraphic forecasts in time to catch outgoing carriers the
service has been given to farmers along their routes. By this
means it has been possible to place in the hands of more than
weather. Snow.