37 CFR 1.166 Specimens.
The applicant may be required to furnish specimens of the plant, or its flower or fruit, in a quantity and at a time in its stage of growth as may be designated, for study and inspection. Such specimens, properly packed, must be forwarded in conformity with instructions furnished to the applicant. When it is not possible to forward such specimens, plants must be made available for official inspection where grown.
Specimens of the plant variety, its flower or fruit, should not be submitted unless specifically called for by the examiner.
Form Paragraph 16.13 may be used to require specimens.
¶ 16.13 Specimens Are Required
Applicant  required to submit  in accordance with 37 CFR 1.166.