Stems very slender, smooth, angled but not winged, weak, 1 to 3 feet long with obliquely ovate or half-sagittate stipules, one-half to 1 inch long, one-third to one-half of an inch wide and toothed; leaflets usually six, varying from four to eight, oval or ovate, pointed and mucronate at the apex, narrowed at the base, three-fourths to 2 inches long, one-fourth to two-thirds of an inch wide, the rachis terminating in a forked tendril. Flowering peduncles as long as the leaves or shorter, with three to nine flowers, yellowish in bud but turning purple as the flower opens; each flower about one-half of an inch long. Fruit a narrow, smooth pod without visible stalk, 1 to 2 inches long and somewhat less than one-fourth of an inch wide.
Memoir 15 N. Y. State Museum
Myrtle-Leaved Marsh Pea - Lathyrus myrtifolius
The members of the genus Lathyrus are often called Vetchlings, because of their close relationship to the true Vetches (genus Vicia), most of which are cultivated or naturalized species in our State. Another native Vetch-ling is the Marsh Vetchling (Lathyrus palustris Linnaeus), a boreal species found in the northern part of the State. It has linear leaflets and the stems are usually winged. The flowers are purple. The Cream-colored Vetchling (Lathyrus ochroleucus Hooker) with rather large cream-colored flowers, and broadly oval, acute leaflets, occurs throughout the western part of the State.