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Title 7: Agriculture
PART 201—FEDERAL SEED ACT REGULATIONS

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purity analysis in the administration of the act

§ 201.45   Obtaining the working sample.

(a) The working sample on which the actual analysis is made shall be taken from the submitted sample in such a manner that it will be representative.

(b) The sample shall be repeatedly divided to the weight to be used for the working sample. Some form of efficient mechanical divider should be used. To avoid damaging large seeds and coated seeds, a divider should be used which will prevent the seeds from falling great distances onto hard surfaces. In case the proper mechanical divider cannot be used or is not available, the sample shall be thoroughly mixed and placed in a pile and the pile shall be repeatedly divided into halves until a sample of the desired weight remains.

[5 FR 32, Jan. 4, 1940, as amended at 20 FR 7929, Oct. 21, 1955; 25 FR 8769, Sept. 13, 1960; 59 FR 64492, Dec. 14, 1994]

§ 201.46   Weight of working sample.

(a) Unmixed seed. The working samples for purity analysis and noxiousweed seed examination of unmixed seed shall be at least the weights set forth in table 1.

(b) Mixtures consisting of one predominant kind of seed or a group of kinds of similar size. The weights of the purity and noxious-weed seed working samples in this category shall be determined by the kind or group of kinds which compromise more than 50 percent of the sample.

(c) Mixtures consisting of two or more kinds or groups of kinds of different sizes, none of which comprise over 50 percent of the sample. The weights of the purity working samples in this category shall be the weighted averages (to the nearest half gram) of the weights listed in table 1 for each of the kinds which comprise the sample determined by the following method: (1) Multiply the percentage of each component in the mixture (rounded off to the nearest whole number) by the sample sizes specified in column 2, table 1, (2) add all these products, (3) total the percentages of all components of the mixtures, and (4) divide the sum in paragraph (c)(2) of this section by the total in paragraph (c)(3) of this section. If the approximate percentage of the components of a mixture are not known they may be estimated. The weight of the noxious-weed seed working sample shall be determined by multiplying the weight of the purity working sample by 10 or by calculating the weighted average in the same manner described above for the purity working sample.

(d) Coated seed.

(1) Unmixed coated seed. Due to variation in the weight of coating materials, the size or weight of the working sample shall be determined separately for each lot. The weight of the working sample shall be determined by weighing 100 completely coated units and calculating the weight of 2,500 coated units for the purity analysis and 25,000 coated units for the noxious-weed seed examination.

(2) Mixtures of coated seed. The working weight shall be determined in the following manner:

(i) Calculate the weight of the working sample to be used for the mixture under consideration as though the sample were not coated by following paragraph (b) or (c) of this section.

(ii) Determine the amount of coating material on 100 coated units by weighing the coated units. Remove the coating material using the methods described in §§201.51b (c) and (d). Calculate the percentage of coating material using the following formulas:

Weight of coating material = weight of 100 coated units − weight of 100 de-coated units;

The percentage of coating material = weight of the coating material divided by the weight of 100 coated units × 100%.

(iii) The weight of the working sample shall be the product of the weight calculated in paragraph (d)(2)(i) of this section multiplied by 100 percent, divided by 100 percent minus the percentage of coating material calculated in paragraph (d)(2)(ii) of this section.

[25 FR 8769, Sept. 13, 1960, and 30 FR 7888, June 18, 1965, as amended at 32 FR 12780, Sept. 6, 1967; 35 FR 6108, Apr. 15, 1970; 41 FR 20156, May 17, 1976; 46 FR 53635, Oct. 29, 1981; 59 FR 64492, Dec. 14, 1994; 65 FR 1707, Jan. 11, 2000]

§ 201.47   Separation.

(a) The working sample shall be weighed in grams to four significant figures and shall then be separated into four parts: (1) Kind or variety to be considered pure seed, (2) other crop seed, (3) weed seed, and (4) inert matter. The components shall be weighed in grams to the same number of decimal places as the working sample. The percentage of each part shall be determined to two decimal places.

(b) Aids for the classification of pure seed, other crop seed, weed seed, and inert matter may include visual examination, use of transmitted light (diaphanoscope), or specific gravity (seed blowers). Specific instructions for classification of the various components are given in §§201.47a to 201.51, inclusive.

(c) The components shall be weighed and percentages calculated as follows:

(1) For sample sizes less than 25 grams, all four components shall be weighed; the percentages shall be based on the sum of these weights and not on the original weight. The sum of these weights shall be compared with the original weight of the working sample as a check against the loss of material, or other errors.

(2) For sample sizes of 25 grams or more, the components—other crop seed, weed seed, and inert matter—shall be weighed separately and their percentages determined by dividing these weights by the original weight of the working sample. The pure seed need not be weighed; its percentage may be determined by subtracting the sum of the percentages of the other three components from 100.

(3) When rounding off the calculated percentages of each component to the second decimal place, round down if the third decimal place is 4 or less and round up if the third decimal place is 5 or more, except that if any component is determined to be present in any amount calculated to be less than 0.015 percent, then that component shall be reported as 0.01 percent. If any component is not found in the purity analysis, then that component shall be reported as 0.00 percent.

(4) The total percentage of all components shall be 100.00 percent. If the total does not equal 100.00 percent (e.g. 99.99 percent or 100.01 percent), then add to or subtract from the component with the largest value (usually the pure seed component).

(d) When the working sample consists of two or more similar kinds or varieties which would be difficult to separate in the entire sample, it is permissible to weigh the similar kinds or varieties together as one component and make the separation on a reduced portion of the sample. At least 400 seeds or an equivalent weight shall be taken indiscriminately from the pure seed component and the separation made on this portion. The proportion of each kind present shall then be determined by weight and from this the percentage in the entire sample shall be calculated.

(e) The Uniform Blowing Procedure described in §201.51a(a) shall be used for the separation of pure seed and inert matter in seeds of Kentucky bluegrass, Canada bluegrass, rough bluegrass, Pensacola variety of bahiagrass, orchardgrass, side-oats grama, and blue grama.

(f) Procedures for purity analysis for coated seed are given in §201.51b.

[25 FR 8770, Sept. 13, 1960, as amended at 30 FR 7890, June 18, 1965; 46 FR 53635, Oct. 29, 1981; 59 FR 64497, Dec. 14, 1994; 65 FR 1707, Jan. 11, 2000]

§ 201.47a   Seed unit.

The seed unit is the structure usually regarded as a seed in planting practices and in commercial channels. The seed unit may consist of one or more of the following structures:

(a) True seeds;

(b) For the grass family:

(1) Caryopses and single florets;

(2) Multiple florets and spikelets in tall oatgrass (Arrhenatherum elatius), oat (Avena spp.), gramas (Bouteloua spp.), rhodesgrass (Chloris gayana), barley (Hordeum vulgare), and bluegrass (Poa spp.);

(3) Entire spikelets in bahiagrass, bentgrasses, dallisgrass, guineagrass, browntop millet, foxtail millet, proso millet, panicgrasses, redtop, rice, switchgrass, and vaseygrass. Entire spikelets which may have attached rachis segments, pedicels, and sterile spikelets in big bluestem, little bluestem, sand bluestem, yellow bluestem, bottlebrush-squirreltail, broomcorn, yellow indiangrass, johnsongrass, sorghum, sorghum- sudangrass, sorghum almum, sorgrass, and sudangrass;

(4) Spikelet groups:

(i) Spikelet groups that disarticulate as a unit in galletagrass;

(ii) Spikelet groups that disarticulate as units with attached rachis and internodes in bluestems, side-oats grama, and yellow indiangrass;

(5) Fascicles of buffelgrass (Cenchrus ciliaris) consisting of bristles and spikelets;

(6) Burs of buffalograss (Buchloe dactyloides);

(7) Bulblets of bulbous bluegrass (Poa bulbosa);

(8) Multiple units as defined in §201.51a(b)(1).

(c) Dry indehiscent fruits in the following plant families: Buckwheat (Polygonaceae), sunflower (Compositae), geranium (Geraniaceae), goosefoot (Chenopodiaceae), and valerian (Valerianaceae);

(d) One- and two-seeded pods of small-seeded legumes (Leguminosae), burs of the burclovers (Medicago arabica, M. polymorpha), and pods of peanuts (Arachis hypogaea). (This does not preclude the shelling of small-seeded legumes for purposes of identification.) Pods of legumes normally containing more than two seeds, when occurring incidentally in the working sample, should be hulled if the kind is hulled when marketed;

(e) Fruits or half fruits in the carrot family (Umbelliferae);

(f) Nutlets in the following plant families: Borage (Boraginaceae), mint (Labiatae), and vervain (Verbenaceae);

(g) “Seed balls” or portions thereof in multigerm beets, and fruits with accessory structures such as occur in other Chenopodiaceae and New Zealand spinach. For forage kochia refer to §201.48(j) and §201.51(a)(7).

[46 FR 53636, Oct. 29, 1981, as amended at 59 FR 64497, Dec. 14, 1994; 65 FR 1707, Jan. 11, 2000]

§ 201.47b   Working samples.

The purity working sample is the sample on which the purity analysis is made. The noxious-weed seed working sample is the sample on which the noxious-weed seed examination is made.

[20 FR 7930, Oct. 21, 1955]

§ 201.48   Kind or variety considered pure seed.

The pure seed shall include all seeds of each kind or each kind and variety under consideration present in excess of 5 percent of the whole. Seeds of kinds or kinds and varieties present to the extent of 5 percent or less of the whole may be considered pure seed if shown on the label as components of a mixture in amounts of 5 percent or less. The following shall be included with the pure seed:

(a) Immature or shriveled seeds and seeds that are cracked or injured. For seeds of legumes (Leguminosae) and crucifers (Cruciferae) with the seed coats entirely removed refer to §201.51(a)(1);

(b) Pieces of seeds which are larger than one-half of the original size. For separated cotyledons of legume seeds refer to §201.51(a)(2);

(c) Insect-damaged seeds, provided that the damage is entirely internal, or that the opening in the seed coat is not sufficiently large so as to allow the size of the remaining mass of tissue to be readily determined. Weevil-infested vetch seeds, irrespective of the amount of insect damage, are to be considered pure seed, unless they are broken pieces one-half or less than the original size. For classification of broken pieces of seed units one-half or less than the original size, refer to §201.51(a)(2). Refer to §201.51(a)(3) for chalcid-damaged seeds;

(d) Seeds that have started to germinate;

(e) Seeds of the cucurbit family (Cucurbitaceae) and the nightshade family (Solanaceae) whether they are filled or empty;

(f) Intact fruits, whether or not they contain seed, of species belonging to the following families: Sunflower (Compositae), buckwheat (Polygonaceae), carrot (Umbelliferae), valerian (Valerianaceae), mint (Labiatae) and other families in which the seed unit may be a dry, indehiscent one-seeded fruit. For visibly empty fruits, refer to inert matter, §201.51(a)(6);

(g) Seed units of the grass family listed in §201.47a(b) (1) through (5) if a caryopsis with some degree of endosperm development can be detected in the units, either by slight pressure or by examination over light. Species in which determination of endosperm development is not necessary are listed in paragraphs (g) (1) and (2) of this section. Refer to §§201.48(h) and 201.51(a)(5) when nematode galls and fungal bodies have replaced the caryopsis in seed units. The following procedures apply to determine pure seed in the grass families listed below:

(1) Intact burs of buffalograss (Buchloe dactyloides) shall be considered pure seed whether or not a caryopsis is present. Refer to §201.51(a)(6) for burs which are visibly empty.

(2) The Uniform Blowing Procedure described in §201.51a(a) shall be used to determine classification of florets into pure seed or inert matter for Kentucky bluegrass, Canada bluegrass, rough bluegrass, Pensacola variety of bahiagrass, side-oats grama, blue grama, and orchardgrass.

(3) Special purity procedures for smooth brome, chewings fescue, red fescue, orchardgrass, fairway crested wheatgrass, standard crested wheatgrass, intermediate wheatgrass, pubescent wheatgrass, tall wheatgrass, and western wheatgrass are listed in §201.51a(b).

(4) For methods of determining pure seed percentages of annual and perennial ryegrass, refer to §§201.58(b)(10) and 201.58a(a).

(h) Seed units with nematode galls, fungal bodies (i.e. ergot, other sclerotia, and smut) and spongy or corky caryopses that are entirely enclosed within the seed unit. Refer to §201.51(c)(1) for inert matter classification.

(i) Seed units of beet and other Chenopodiaceae, and New Zealand spinach. Refer to §201.47a(g) and §201.51(a)(6) for definitions of seed units and inert matter, respectively.

(j) Seed units of forage kochia that are retained on a 1 mm opening square-hole sieve, when shaken for 30 seconds. For inert matter, refer to §201.51(a)(7).

[46 FR 53636, Oct. 29, 1981, as amended at 59 FR 64497, Dec. 14, 1994]

§ 201.49   Other crop seed.

(a) Seeds of plants grown as crops (other than the kind(s) and variety(ies) included in the pure seed) shall be considered other crop seeds, unless recognized as weed seeds by applicable laws, or regulations, or by general usage. All interpretations and definitions for “pure seed” in §201.48 shall also apply in determining whether seeds are “other crop seed” or “inert matter” with the following two exceptions which may be applied as acceptable alternatives:

(1) Uniform Blowing Procedure in §201.51a(a) for kinds listed in §201.47(e) may be disregarded. If disregarded, all seed units (as defined in §201.47a) for these kinds found in the working sample shall be manually separated into pure seed and inert matter. Only units containing at least one caryopsis with some degree of endosperm development which can be detected either by slight pressure or by examination over light are considered other crop seed.

(2) Multiple Unit Procedure in §201.51a(b) for kinds listed in §201.48(g)(3) may be disregarded. If disregarded, all multiple units and single units (as defined in §201.51a(b)) for these kinds found in the working sample shall be manually separated into single florets. Each floret containing a caryopsis with some degree of endosperm development, which can be detected either by slight pressure or examination over light, is considered other crop seed. Empty florets and glumes, if present, are considered inert matter. Refer to §201.51(a)(4).

(b) [Reserved]

[59 FR 64498, Dec. 14, 1994; 60 FR 2493, Jan. 10, 1995]

§ 201.50   Weed seed.

Seeds (including bulblets or tubers) of plants shall be considered weed seeds when recognized as weed seeds by the law or rules and regulations of the State into which the seed is offered for transportation or transported; or by the law or rules and regulations of Puerto Rico, Guam, or District of Columbia into which transported, or District of Columbia in which sold; or found by the Secretary of Agriculture to be detrimental to the agricultural interests of the United States, or any part thereof. Damaged weed seeds and immature seedlike structures, as described in §201.51(b), shall be considered inert matter. Weed seeds, as defined above in this section, requiring further separation into weed seed and inert matter components are as follows:

(a) The individual seeds are to be removed from fruiting structures such as pods and heads. The seeds are classified as weed seed and the remaining fruiting structures classified as inert matter.

(b) Wild onion and wild garlic ( Allium spp.) bulblets that have any part of the husk remaining and are not damaged at the basal end are considered weed seeds regardless of size. Bulblets that are completely devoid of husk, and are not damaged at the basal end, and are retained by a1/13-inch (1.9 mm) round-hole sieve are considered weed seeds. For wild onion and wild garlic ( Allium spp.) bulblets classed as inert matter, refer to §201.51(b)(5).

[46 FR 53636, Oct. 29, 1981, as amended at 59 FR 64498, Dec. 14, 1994; 65 FR 1707, Jan. 11, 2000]

§ 201.51   Inert matter.

Inert matter shall include seeds and seed-like structures from both crop and weed plants and other material not seeds as follows:

(a) Seeds and seed-like structures from crop plants:

(1) Seeds of legumes (Leguminosae) and crucifers (Cruciferae) with the seed coats entirely removed. Refer to §210.48(a) for pure seed classification.

(2) Pieces of broken and damaged seed units, including those that are insect damaged, which are one-half the original size or less. If greater than one-half, refer to §201.48(b) and (c) for pure seed classification. Also included as inert matter are separated cotyledons of legumes, irrespective of whether or not the radicle-plumule axis and/or more than one-half of the seed coat may be attached.

(3) Chalcid-damaged seeds (puffy, soft, or dry and crumbly) of alfalfa, red clover, crimson clover, and similar kinds of small seeded legumes. Refer to §201.48(c) for pure seed classification.

(4) Glumes and empty florets except as stated under pure seed. Refer to §201.48 (g) and (h) for pure seed classification.

(5) Seed units with nematode galls or fungal bodies (smut, ergot, and other sclerotia) that are not entirely enclosed within the seed unit. Refer to §201.48(h) for pure seed classification.

(6) Broken seed units of Chenopodiaceae and fruit portions or fragments of monogerm beets, New Zealand spinach, buffalograss, and families in which the seed unit is a dry indehiscent one-seeded fruit that visibly do not contain a seed. Refer to §201.48 (f), (g)(1), (i), and (j) for pure seed classification.

(7) Seed units of forage kochia that pass through a 1 mm opening, square-hole sieve, when shaken for 30 seconds.

(8) The thin pericarp (fruit wall), if present on seeds of northern sweetvetch.

(b) Seeds and seed-like structures from weed plants, which by visual examination (including the use of light or dissection), can be determined to be within the following categories:

(1) Damaged seed (other than grasses) with over one-half of the embryo missing.

(2) Grass florets and caryopses classed as inert:

(i) Glumes and empty florets of weedy grasses;

(ii) Damaged grass caryopses, including free caryopses, with over one-half the root-shoot axis missing (the scutellum excluded);

(iii) Immature free caryopses devoid of embryo and/or endosperm;

(iv) Immature florets of quackgrass (Agropyron repens) in which the caryopses are less than one-third the length of the palea. The caryopsis is measured from the base of the rachilla;

(v) Free caryopses of quackgrass (A. repens) that are 2 mm or less in length.

(3) Seeds of legumes and species of Brassica with the seed coats entirely removed.

(4) Immature seed units, devoid of both embryo and endosperm, such as occur in but not limited to the following plant families: Sedge (Cyperaceae), buckwheat (Polygonaceae), morning glory (Convolvulaceae), nightshade (Solanaceae), puncturevine (Zygophyllaceae) and sunflower (Compositae). Cocklebur (Xanthium spp.) burs are to be dissected to determine whether or not seeds are present.

(5) Wild onion and wild garlic (Allium spp.) bulblets:

(i) Bulblets which are completely devoid of the husk and pass through a

1/13th-inch, round-hole sieve.

(ii) Bulblets which show evident damage to the basal end, whether husk is present or absent. Refer to §201.50(c) for wild onion and wild garlic (Allium spp.) bulblets classed as weed seeds.

(6) Dodder (Cuscuta spp.): Seeds devoid of embryos and seeds which are ashy gray to creamy white in color are inert matter. Seeds should be sectioned when necessary to determine if an embryo is present as when seeds have a normal color but are slightly swollen, dimpled or have minute holes.

(7) Buckhorn (Plantago lanceolata): Black seeds, with no brown color evident, whether shriveled or plump; the color of questionable seeds shall be determined by use of a stereoscopic microscope with magnification of approximately 10× and a fluorescent lamp with two 15-watt daylight-type tubes.

(8) Ragweed (Ambrosia spp.): Seed with both the involucre and pericarp absent.

(c) Other matter that is not seed:

(1) Free nematode galls or fungal bodies such as smut, ergot, and other sclerotia.

(2) Soil particles, sand, stone, chaff, stems, leaves, flowers, loose coating material, and any other foreign material.

(3) Coating material removed from coated seed by washing. Refer to §201.51b(c).

[46 FR 53637, Oct. 29, 1981; 46 FR 58059, Nov. 30, 1981; 59 FR 64498, Dec. 14, 1994; 65 FR 1707, Jan. 11, 2000]

§ 201.51a   Special procedures for purity analysis.

(a) The Uniform Blowing Procedure shall be used for the separation of pure seed and inert matter in the following: Kentucky bluegrass, Canada bluegrass, rough bluegrass, Pensacola variety of bahiagrass, orchardgrass, blue grama, and side-oats grama.

(1) When kinds listed in this section appear in mixtures they shall be separated from other kinds before using the Uniform Blowing Procedure.

(2) To determine the blowing point for these procedures, individual calibration samples for Kentucky bluegrass, orchardgrass, and Pensacola variety of bahiagrass shall be used. The calibration sample for Kentucky bluegrass shall be used for Canada bluegrass, rough bluegrass, blue grama, and side-oats grama.

(i) The blowing point for Canada bluegrass shall be the same as the blowing point determined for Kentucky bluegrass.

(ii) The blowing point for rough bluegrass shall be a factor of 0.82 (82 percent) of the blowing point determined for Kentucky bluegrass. The 0.82 factor is restricted to the General-type seed blower.

(iii) The blowing point for blue grama shall be a factor of 1.157 of the blowing point determined for Kentucky bluegrass. Before blowing, extraneous material that will interfere with the blowing process shall be removed. The sample to be blown shall be divided into four approximately equal parts and each blown separately. The 1.157 factor is restricted to the General-type seed blower.

(iv) The blowing point for side-oats grama shall be a factor of 1.480 of the blowing point determined for Kentucky bluegrass. Before blowing, extraneous material that will interfere with the blowing process shall be removed. The sample to be blown shall be divided into four approximately equal parts and each part blown separately. The 1.480 factor is restricted to the General-type seed blower.

(3) Calibration samples and instructions are available on loan through the Seed Regulatory and Testing Branch, LS, AMS, Building 306, Room 213, Beltsville, Maryland 20705.

(4) The calibration samples shall be used to establish a blowing point prior to proceeding with the separation of pure seed and inert matter for these kinds. After completing the blowing procedure, remove all weed and other crop seeds from the light portion and add these to the weed or other crop separation, as appropriate. The remainder of the light portion shall be considered inert matter. Remove all weed and other crop seeds and other inert matter (stems, leaves, dirt) from the heavy portion and add these to the weed seed, other crop seed, or inert matter separations, as appropriate. The remainder of the heavy portion shall be considered pure seed.

(5) With orchardgrass, after the blowing, proceed with the multiple unit procedure.

(b) The Multiple Unit Procedure of determining the pure seed fraction shall be used only for the kinds included in the following table when multiple units are present in a sample. These methods are applicable to the kinds listed when they occur in mixtures or singly. Any single unit without attached structures, as described below, shall be considered a single unit. Multiple units and single units for the kinds listed shall remain intact. The attached glumes and fertile or sterile florets shall not be removed from the fertile floret.

(1) A multiple unit is a seed unit that includes one or more structures as follows (the length of the awn shall be disregarded when determining the length of a fertile floret or an attached structure):

(i) An attached sterile or fertile floret that extends to or beyond the tip of a fertile floret;

(ii) A fertile floret with basally attached glume, glumes, or basally attached sterile floret of any length;

(iii) A fertile floret with two or more attached sterile and/or fertile florets of any length.

(2) Procedure for determination of multiple units:

(i) For the single kind: determine the percentage of single units present, based on the total weight of single units and multiple units. Apply the appropriate factor, as determined from the following table, to the weight of the multiple units and add that portion of the multiple unit weight to the weight of the single units. The remaining multiple unit weight shall be added to the weight of the inert matter.

(ii) For mixtures that include one or more of the kinds in the following table, determine the percentage of single units, based on the total weight of single units and multiple units, for each kind. Apply the appropriate factor as determined from the following table, to the weight of multiple units of each kind.

[59 FR 64498, Dec. 14, 1994]

§ 201.51b   Purity procedures for coated seed.

(a) The working sample for coated seed is obtained as described in §201.46(d) (1) and (2), and weighed in grams to four significant figures.

(b) Any loose coating material shall be sieved, weighed, and included with the inert matter component.

(c) Coating material is removed from the seed by washing with water or other solvents such as, but not limited to, dilute sodium hydroxide (NaOH). Use of fine mesh sieves is recommended for this procedure, and stirring or shaking the coated units may be necessary to obtain de-coated seed.

(d) Spread de-coated seed on blotters or filter paper in a shallow container. Air dry overnight at room temperature.

(e) Separation of component parts:

(1) Kind or variety considered pure seed.

(2) Other crop seed.

(3) Inert matter.

(4) Weed seed.

(f) The de-coated seed shall be separated into four components in accordance with §§201.48 through 201.51. §§201.51a (a) and (b) shall not be followed. The weight of the coating material is determined by subtracting the sum of the weights of the other four components from the original weight of the working sample. The percentage of coating material shall be included with the inert matter percentage. Calculate percentages of all components based on the original weight of the working sample (see paragraph (a) of this section).

[59 FR 64499, Dec. 14, 1994]

§ 201.52   Noxious-weed seeds.

(a) The determination of the number of seeds, bulblets, or tubers of individual noxious weeds present per unit weight should be made on at least the minimum quantities listed in §201.46 Table 1: Provided, That if the following indicated numbers of a single kind of seed, bulblet, or tuber are found in the pure seed analysis (or noxious-weed seed examination of a like amount) the occurrence of that kind in the remainder of the bulk examined for noxious-weed seeds need not be noted:1/2-gram purity working sample, 16 or more seeds; 1-gram purity working sample, 23 or more seeds; 2-gram purity working sample or larger, 30 or more seeds. The seeds per unit weight shall be based on the number of single seeds. The number of individual seeds shall be determined in burs of sandbur ( Cenchrus spp.) and cocklebur ( Xanthium spp.); in capsules of dodder ( Cuscuta spp.); in berries of groundcherry, horsenettle, and nightshade (Solanaceae); and in the fruits of other noxious weeds that contain more than one seed. Refer to §§201.50 and 201.51(b)(4) for the classification of weed seeds and inert matter, respectively.

(b) A noxious-weed seed examination of coated seed samples shall be made by examining approximately 25,000 units obtained in accordance with §201.46(d) and which have been de-coated by the method described in §201.51b(c).

[59 FR 64499, Dec. 14, 1994]

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