Monographs Details: Chamaecrista rotundata var. interstes 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:Variety Description - Habit of var. rotundata, but blades of stipules and lfts smaller, the stipules as described in diagnosis, the lfts commonly 3-4, rarely up to 7 pairs, ovate to ovate- oblong, 4.5-12 x 2.5-5 mm.-Collections: 9. [Key: "Stipules either broadly low-deltate at tip or rounded at tip or rounded as in the preceding, but if the latter then smaller, 7-14(-15) X 5-12 mm and in any case only 17-25-nerved from point of attachment; if sympatric with the last then the stipule-tips deltate. Blade of stipules ovate, at apex broadly low-delatate; centr. Sa. do Espinhaco, within the range of var. grandistipula."]

Distribution and Ecology - Cerrado and stony campo, commonly on white or gray quartzite sands, 790-1200 m, known only from the headwaters of R. Jequetinonha between Diamantina and Mendanha, centr. Minas Gerais.—Fl. IV-VI.

Discussion:In form of the stipules, narrowly membranous-margined as in other forms of Ch. rotundata but incipiently acute and smaller than those of sympatric var. grandistipula, this newly described variety suggests morphological passage between its species and the closely related, also sympatric Ch. distichoclada. By shifting emphasis from the small vegetative difference to the shared habit, flower and fruit, essentially identical throughout the group, a case could be developed for considering these species, as well as Ch. potentilla and perhaps Ch. cinerascens, as deviant expressions of one major type, differing one from the next in shape of stipules and in size and number of leaflets. However, despite an essential sympatry within a radius of some 30 kilometers of Diamantina, and no known ecological separation, we have no evidence that the two varieties of Ch. rotundata, Ch. distichoclada and Ch. potentilla are connected by a clinal series of intermediate forms; they emerge, on the contrary, as small, weakly but exactly differentiated entities. Furthermore the difference between the extreme forms, Ch. potentilla on the one hand, with its many tiny leaflets and small, firm-margined, acuminate stipules, and Ch. rotundata var. grandistipula on the other, with few ample leaflets accompanied by suborbicular, membranous-margined stipules, is altogether too great to be compressed within a convenient specific concept.
Distribution:Minas Gerais Brazil South America|