Monographs Details: Chamaecrista serpens var. isthmogenes H.S.Irwin & Barneby
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 2: 455-918.
Description:Variety Description - Stems prostrate from suffruticulose caudex, 1-2 dm, together with foliage either pilosulous and setose or only thinly setose; stipules 2.5-6 x 0.4-l(-1.4) mm; lvs 10-22 mm; lfts 3—5(—6) pairs, the larger ones obliquely obovate very obtuse 4-9 x 3-6.3 mm, 1.5-2 times as long as wide, sharply coarsely venulose on both faces; fls relatively large, the long petal 11-15 mm, the longer anthers 4-6 mm; style 5-7 mm.—Collections: 6. [Key: "Fl larger, the asymmetric petal 9-19(-20) mm, the longer anthers to 4-9.5 mm, the style (4-)4.5-10 mm; discontinuously dispersed from s. Arizona to n. Argentina. Lfts of larger lvs 3-7(-8) pairs; s. Mexico (Puebla, Oaxaca); Central America (Honduras and Nicaragua); South America (middle Orinoco valley to Argentina, localized and discontinuous). Lfts of broader outline, the widest of larger lvs (2.5-)2.7-6 mm wide. Petiolar gland l-several; either lowland Oaxaca, or highland Central America. Gland solitary; larger lfts relatively very broadly very broad, 4-9 X3-6 mm, only 1.5-2 times as long as wide, coarsely shrply venulose; s. Oaxaca below 200 m."]

Distribution and Ecology - Rocky hillsides overlooking the Pacific Ocean, in open places in low deciduous brush-woodland, 5-140 m, known only from the coastal hills 1-5 km w.-ward from Salina Cruz in distr. Tehuantepec and from one station ±160 km distant along the immediate coast of distr. Pochutla (Barra de Sta. Elena, a glabrate form), Oaxaca.—Fl. IX-XII.

Discussion:The var. isthmogenes differs from all other forms of Ch. serpens in its broad veiny leaflets which endow it with a strongly individual facies. Near Salina Cruz it is a member of a xeromorphic coastal scrub flora which includes several locally endemic Leguminosae, among them Mimosa sousae Grether, Acacia deamii Standl. and Dalea sousae Barneby.
Distribution:Oaxaca Mexico North America|