This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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..
Annual branching herbs, with opposite leaves, and small white yellow violet or variegated flowers, solitary in the upper axils, or in terminal bracted spikes. Calyx 4-toothed, the 2 upper teeth somewhat the longer. Corolla irregular, 2- lipped, the tube narrow, gradually enlarged above, the upper lip compressed, obtuse or emarginate with a groove behind the margins, or these recurved or with a tooth on each side; lower lip spreading or ascending, 3-toothed, 2-grooved beneath. Stamens 4, didynamous, ascending under the upper lip; anther-sacs distinct, parallel obtuse or mucronulate at the base. Capsule flat, oblique, loculicidally dehiscent, 2-4-seeded. Seeds smooth, strophiolate. [Greek, black wheat.]
About 10 species, all of the northern hemisphere. Only the following are known in North America. Type species: Melampyrum arvense L.
Leaves lanceolate or linear-lanceolate, the floral 2-4-toothed at the base; capsule much longer than wide, long-beaked.
1. M. lineare.
Leaves ovate, all entire; capsule slightly longer than wide, short-beaked.
2. M. latifolium.
Puberulent; stem slender, obscurely 4-sided above, at length widely branched, 6'-1 1/2° high. Leaves lanceolate or linear-lanceolate to ovate, short-petioled, acuminate or acute at the apex, narrowed, obtuse, or the upper truncate at the base, l'-2 1/2' long, 1 1/2"-6" wide, the lower entire, the upper floral ones ovate or lanceolate, with 2-6 bristle-pointed teeth near the base or entire; flowers short-peduncled, 4"-6" long; calyx about one-third the length of the corolla, its subulate teeth longer than its tube; corolla white or whitish, puberulent, the lower lip yellow; capsule 4"-5" long, about 2" wide, twice as long as the calyx, long-beaked.
In dry woods and thickets, Nova Scotia to British Columbia, south to Georgia, Tennessee, Iowa, Montana and Idaho. Consists of several races, differing in leaf-form. Ascends 3500 ft. in Virginia. May- Aug.
Melampyrum latifolium Muhl. Cat. 57. 1813.
Similar to the preceding, widely branched, 1°-1 1/2° high; but the leaves all entire, short-petioled, the lowest small, spatulate, obtuse, the middle ones lanceolate or ovate, acuminate, narrowed at the base, 2'-3' long, the floral ovate or ovate-lanceolate, shorter, acute, mostly rounded at the base; corolla purple, veiny, larger; capsule little longer than wide, short-beaked.
In dry woods, Delaware (according to Muhlenberg); mountains of Virginia to Georgia and Tennessee. June-Aug.