Monographs Details: Cassia linearifolia G.Don
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1978. Monographic studies in Cassia (Leguminosae, Caesalpinioideae). III. Sections Absus and Grimaldia. Mem. New York Bot. Gard. 30: 1-300.

A species easily recognized by the completely glabrous, glutinous stems and foliage, bifoliolate leaves, and narrow grasslike leaflets that ascend vertically, turned half face to face, from the tips of the narrowly ascending, ventrally grooved petiole. The erect attitude of the leaflets distinguishes C. linearifolia from the related and habitally similar C. incurvata, in which the leaflets, always of broader and more oblique outline, are turned outward and downward to point obliquely earthward. The also related C. planifolia and C. lavradiodes, while similar in the erect unijugate leaflets, differ in the shorter, more widely winged petiole and either obliquely ovate or obovate-cuneate blades. The remotely allopatric C. crommyotricha resembles C. linearifolia in the often narrow and erect leaflets, but these are always four in some leaves, and the plant differs further in its more amply paniculate inflorescence commonly not only verruculose but minutely setulose.

The six known collections of C. linearifolia, which seems to be rare and highly localized, fall into two groups, one with extremely narrow, truly grasslike leaflets and petals about as long as the sepals, the other with broader leaflets and exserted petals. The narrow-leaved type is known certainly only from Sorocaba, about 90 km west of Sao Paulo; the broader-leaved one, which has been described as C. bradei, from within a 50 km radius north of the city and disjunctly in southeastern Minas Gerais. In the context of the section, in which local endemism is so highly developed, these two forms deserve varietal status.

1. Leaflets linear-elliptic, attenuate toward both ends, 2.5-4.5 mm wide and ±14-18 times longer than wide.

133a. var. linearifolia

1. Leaflets narrowly elliptic, attenuate toward the base but more abruptly acuminate at apex, (6)7-15(17) mm wide and ±3.5-7 times longer than wide.

133 b. var. bradei