This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Leafy-stemmed plants, from a cluster of thick fibrous roots. Flowers small, greenish, in a long open spike with long bracts. Sepals and petals broad, spreading. Lip lanceolate, with a tooth on each side and a tubercle at the middle of the base or nearly orbicular. Spur slender, straight, longer than the lip, but shorter than the ovary. Valves of the anthers horizontal, opening upward, dilated at the base so as to form an oblong cavity, enclosing the orbicular incurved gland. Pollinia granulose, produced at the base into a caudicle. [Latin, a little wallet]
Orchis flava L. Sp. PI. 942. 1753.
Orchis virescens Willd. Sp. PI. 4: 37. 1805.
H. flava A. Gray, Am. Journ. Sci. 38: 308. 1840.
P. flava Farwell, Ann. Rep. Parks Detroit 11:54. 1900.
Stem rather stout, 1°-2° high, leafy. Leaves lanceolate or elliptic, acute or obtuse, 4'-12' long, 8"-3' wide; spike 2'-6' long; bracts acuminate, longer than the ovaries; petals greenish; sepals and petals ovate or roundish, about 3" long; sepals greenish yellow, lip a little longer than the petals, entire or crenulate, mostly with an obtuse tooth on each side and a tubercle at the middle of the base; anther-sacs parallel, the sides forming a rounded cavity, in which lie the orbicular incurved glands; capsule about 4" long.