Monographs Details: Chamaecrista rufa var. exsul 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.
Family:Caesalpiniaceae
Description:Latin Diagnosis - Chamaecrista rufa (Martens & Galeotti) Britton & Rose var. exsul Irwin & Barneby, var. nov., a var. rufa imprimis florum parvulorum sepalis 5.5-7.5 (nec 8.5-13.5) mm, petalo abaxiali majori 8-9.5 (nec 10-19) mm longis, foliolis fere semper magis numerosis 32-45 (nec 18-32)- jugis usque, patriaque procul distanti diversa.-BRAZIL. Mato Grosso: Os Dardanelos, Rio Aripuaná, 15.VI. 1974 (fl, fr), Manoel dos R. Cordeiro 68.

Species Description - Suffruticose becoming shrubby, at anthesis 5-20 dm, the branchlets and lf- stalks incurved-puberulent and sometimes incipiently setulose with incurved-ascending hairs; gland 0.4-0.8 mm diam, either stipitate or subsessile, the short stipe slender or columnar, the whole in profile drum-shaped, obconical, or squatly tack-shaped, 0.4 mm shorter to 0.2 mm longer than the head; longer lfts of major lvs inserted 2-3 mm apart along rachis, up to 10-15 x 1.2-2.2(-2.4) mm; otherwise as given in key.—Collections: 4.

Distribution and Ecology - Scrub savanna and secondarily in capoeira replacing high Amazonian forest on terra firme, below 300 m, known only from tributaries of the upper Madeira (Jaciparaná; Rio Jamari) and Aripuanã rivers in Terr. Rondônia and n.-w. Mato Grosso, lat. ±9-10°S, Brazil.—Fl. IV-X.

Discussion:

The var. exsul, so named for its occurrence in places and environments unexpectedly remote from the main focus of Ch. rufa in Mexico and Central America, is the only Brazilian chamaecrista other than Ch. flexuosa with as many as 32-45 pairs of very narrow leaflets, and readily distinguished from that by the asymmetric venulation of the blades and by the small supra-axillary flowers. It simulates puberulent states of var. rufa closely, but differs nearly always in the more numerous leaflets of larger leaves and consistently, so far as our data go, in flower size. Moreover the midrib of the leaflets tends to be slightly less displaced, becoming intramarginal by 0.2-0.5 mm. But rare individual plants of var. rufa from Veracruz (e.g. Purpus 1882, GH) have up to 39 pairs of leaflets in the largest leaves and we find in the same region some overlap in the position of the midrib relative to the distal margin. The major secondary venules arising from the midrib on the blade’s proximal side are generally 5-9 in var. exsul, 2-6 (but mostly 3—5) in var. rufa. It is especially interesting to find among the four known collections of var. exsul, certainly conspecific in a very narrow sense and sympatric with no kindred species from which alien characters could be derived by introgression, a substantial variation in the petiolar glands, the short stipe of which varies from slender to stout and columnar, yielding in profile a tack-shaped, drum-shaped or intermediately obconical figure. Here certainly, as probably else where, variation in the gland is inherent in the constitution of the chamaecristae verae.

Distribution:Brazil South America| Mato Grosso Brazil South America| Rondônia Brazil South America|