Monographs Details: Senna guatemalensis var. hidalgensis 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 1: 1-454.
Description:Variety Description - Thinly strigulose-pilosulous with hairs to 0.6-1.2 mm, the basal angle of midrib on dorsal side of lfts always more densely pilose; gland between proximal pair of lfts only; long lfts broadly obovate or elliptic-obovate 3-7 x 2-3.7 cm, ±1.5-2 times as long as wide; racemes and fls of var. guatemalensis except the sepals less strongly graduated, the outer 4-5 mm, the inner 5.5-6 mm long; longer petals 8-11.5 mm; style 0.7-1 mm; stipe of pod ±2 mm, the body 6.5-8 x 0.8-1.1 cm, the interseminal septa 0.5-1 mm high.—Collections: 7. [Key: "Racemes 20-70-fld, the fruiting axis 3-16 cm; s.-centr. Guatemala and n.-w. into Mexico.2. Lfts 6-9 pairs; pod 9.5-12 mm wide; areole of seed-face 2-3.5 mm wide; highland Guatemala, from Sa. de Cuchumatanes to dept. Chimaltenango. Lfts 3-6(-7) pairs; allopatric, and if pod as wide then the areole narrower; Mexico. Lfts obovate, obtuse or emarginate; Hidalgo, Puebla, Chiapas. Fls larger, the longest sepal 5-6 mm, the longest petal 8-11.5 mm. Pod larger, ±6.5-8 x 0.8-1.1 cm; local in n.-w. Hidalgo, Mexico."]

Distribution and Ecology - Mixed pine-oak-juniper woodland, coming out onto roadsides, ±1900-2500 m, local on the Gulf slope of Sa. Madre Oriental, in drainage of Rio Moctezuma, n.-w. Hidalgo.—Fl. VII-VIII.

Discussion:A combination of solitary petiolar glands, 3-5 pairs of ample obovate leaflets and the inflorescence of var. guatemalensis neatly characterize this local Mexican senna. The pod is exactly that of var. guatemalensis except for the internal development of distinct cross-walls between the individual seed-cavities, and the seed itself is marked by a narrower areole 1-1.5 (not 2-3.5) mm wide. Probably more closely related are the geographically nearer vars. scopulorum and calcarea, both of which have solitary petiolar glands. For differences see discussion of the varieties preceding and following. The var. hidalgensis was collected first in Mexico, very likely near Zimapan by Thomas Coulter. The specimens (K), which now lack locality data, were referred by Bentham (1871, p. 541) to his mixed concept of Cassia botteriana and said to have originated in Nayarit ("between San Bias and Tepic").
Distribution:Hidalgo Mexico North America|