Monographs Details: Ditremexa occidentalis (L.) Britton & Rose ex Britton & P.Wilson
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - A tall, upright, herbaceous plant, annual or perennial in duration, common in open situations throughout tropical and warm-temperate America, ranging north to Virginia, Indiana and Missouri, and introduced into tropical parts of the Old World, with once-compound leaves, and axillary, yellow flowers. In Porto Rico it is common in fields, on banks, and in waste and cultivated grounds, sometimes a weed, at lower and middle elevations, ascending to about 500 meters;
also on the small islands Desecheo, Mona, Vieques and Cayo Icacos. Stinking-weed is another English name, the plant being unpleasantly odorous.
Ditremexa (derivation of the name unexplained) was established a genus by Rafinesque in 1838, the species here illustrated typical; the number of species is large, natives of tropical and temperate regions, mostly herbs and shrubs. They have once-compound leaves, with a gland near the base of the leaf-stalk, the yellow, clustered flowers axillary, or terminal. The 5 sepals are usually blunt, the 5 petals nearly alike; there are usually 7, perfect stamens, the anthers opening by terminal pores, and 5 imperfect ones (staminodes); the 1-celled ovary contains many ovules. The narrow, mostly flattened pods split into 2 valves, releasing the transverse or oblique seeds.
Ditremexa occidentalis (western) is smooth, or sparingly hairy, about 2 meters high, or lower. The long-stalked leaves bear a large, round gland near the base of the stalk; there are from 4 to 6 pairs of thin, pointed, ovate to lance-shaped, short-stalked leaflets, about 7 centimeters long, or shorter. The flowers are few, in short-stalked, axillary clusters, with lance-shaped bracts from 10 to 15 millimeters long, which early fall away; the sepals are from 6 to 9 millimeters long, the yellow petals, fading white, about twice as long as the sepals.The pod, usually a little curved, is from 6 to 12 centimeters long, from 6 to 9 millimeters wide, with thickened margins.The flattened, obovoid, brown, dull seeds are about 4 millimeters long.
Another species, Ditremexa hirsuta, is also illustrated in this work.
Cassia occidentalis Linnaeus, Species Plantarum 377. 1753.
Ditremexa occidentalis Britton & Rose; Britton & Wilson, Scientific Survey of Porto Rico and the Virgin islands 5: 372. 1924.