Monographs Details: Chamaecrista serpens var. oaxacana 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 1-2.5 dm from suffruticulose caudex; stipules (2-)3-5 x 1.5-2 mm, shallowly cordate on side further from petiole; lvs 12-20 mm; lfts 5-7 pairs, the larger ones obliquely oblong-elliptic 5-7 x 1.5-2.5 mm, 2.8-4.2 times as long as wide, sharply coarsely venulose on both faces; fls relatively large, the longest petal 12-14 mm, the longer anthers 4.5-6.5 mm; style 4-6.5 mm.—Collections: 7. [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 relatively narrow outline, the wideset of a plant mostly less than 2.5 mm broad. Petiolar gland usually 1; either Mexico or S. America. Venulation of lfts coarsely sharply prominulous; stipules 1.5-2 mm wide, incipiently cordate basally on side further from petiole; s. Puebla and n. Oaxaca, Mexico, 1400-1700 m."]

Distribution and Ecology - Open places in low deciduous brush-woodland, on red lateritic or calcareous soils, 1400-1750 m, narrowly localized in seasonally arid hill-country of n.-w. Oaxaca (distr. Huajuapan) and immediately adjacent Puebla (mun. Chila), Mexico.—Fl. VI-VIII.

Discussion:This variety and the next following, both highly localized in southern Mexico, seem to have arisen as locally modified races of the more widely dispersed var. wrightii, from which they differ collectively in the fewer pairs of leaflets. In leaflet number they resemble var. grandiflora, but differ in the coarsely prominent venulation and remotely allopatric distribution. The relatively broad stipules of var. oaxacana, which may be distinctly cordate at base on the side further from the associated petiole, and the proportionately narrow leaflets distinguish it from lowland maritime var. isthmogenes.
Distribution:Oaxaca Mexico North America| Puebla Mexico North America|