(b) The tolerance applicable to the prohibition of the noxious weed seeds listed in paragraph (a)(2) of this section shall be two seeds in the minimum amount required to be examined as shown in column 1 of table 1 of § 361.5. If fewer than two seeds are found in an initial examination, the shipment from which the sample was drawn may be entered. If two seeds are found in an initial examination, a second sample must be examined. If two or fewer seeds are found in the second examination, the shipment from which the samples were drawn may be entered. If three or more seeds are found in the second examination, the shipment from which the samples were drawn may not be entered. If three or more seeds are found in an initial examination, the shipment from which the sample was drawn may not be entered.
(c) Any seed of any noxious weed that can be determined by visual inspection (including the use of transmitted light or dissection) to be within one of the following categories shall be considered inert matter and not counted as a weed seed:
(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 caryopses, including free caryopses, with over one-half the root-shoot axis missing (the scutellum excluded);
(iii) Immature free caryopses devoid of embryo or endosperm;
(iv) Free caryopses of quackgrass (Elytrigia repens) that are 2 mm or less in length; or
(v) Immature florets of quackgrass (Elytrigia 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.
(3) Seeds of legumes (Fabaceae) 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: buckwheat (Polygonaceae), morning glory (Convolvulaceae), nightshade (Solanaceae), and sunflower (Asteraceae).
(5) Dodder (Cuscuta spp.) seeds devoid of embryos and seeds that are ashy gray to creamy white in color are inert matter. Dodder seeds should be sectioned when necessary to determine if an embryo is present, as when the seeds have a normal color but are slightly swollen, dimpled, or have minute holes.