Senna hirsuta var. puberula

Cassia longisiliqua Blanco, Fl. Filip. 338. 1837.—"[Islas Filipinas, probably Luzon:] . . . en todas partes en las orillas de los caminos."—No typus survives, but the description and discussion decisive.—C. sulcata Blanco, Fl. Filip, ed. 2, 236. 1845, substituted for the preceding, a posterior homonym of C. longisiliqua Linnaeus, but itself also a posterior homonym of C. sulcata DC.—Inexactly equated by Merrill, Bur. Sci. Publ. 12: 173. 1918, with C. hirsuta Linnaeus.

Cassia leptocarpa var. hirsuta sensu Bentham, 1870, p. 112, quoad pl. boliv., non var. hirsuta sens, restr. quae = S. hirsuta var. hirta; De Wit, 1955, p. 251, quoad pl. philippin.

Cassia hirsuta sensu Chodat & Hassler, 1904, l.c.; Merrill, Philipp. J. Sci. Bot. 5: 50. 1910 Enum. Philipp. Fl. 2: 263. 1923; Burkart, 1952, p. 165.

Cassia pubescens sensu Chodat & Hassler, 1904, l.c.

Strigulose or incurved-pilosulous with hairs to 0.4-0.7 mm (random ciliae sometimes to 0.9 mm), the lfts pubescent on both faces; petiole (2-)2.5-5 cm; rachis 5.5-12(-15.5) cm; gland ovoid, taller than wide; lfts 4-6(-7) pairs, the distal pair broadly ovate- to lance-acuminate 4.5-8 x 1.3-3 cm, (1.9-)2.3-4.3 times as long as wide; peduncles 2-12 mm; racemes 2-14-fld, the axis including peduncle becoming (4-)6-30 mm; longer sepals 7-10 mm; petals up to 12-16 mm; ovules ±66-82; pod 15-25 x 0.3-0.5(-0.55) cm, simply curved outward, the valves either strigulose or hirsutulous.—Collections: 21.

Disturbed semideciduous or moist evergreen woodland, campo thickets, fields and waste places, mostly 200-550 m but ascending in Bolivia (Cochabamba), perhaps only adventively, to 2000 m, locally frequent along the Andean piedmont and adjoining plains from the headwaters of Rio Mamore in s.-centr. Bolivia to those of Rios Salado and Dulce in Tucuman and adjoining Santiago del Estero, n.-w. Argentina, thence e. across the Gran Chaco to the Brazilian frontier in Paraguay, to be expected in extreme s. Mato Grosso.—Fl. XII-V.—Taperigua (Argentina).

The var. puberula stands intermediate, both morphologically and geographically, between vars. hirta and streptocarpa, having the simply arched (not twisted) pod and, often but not always, the few-flowered raceme of the former, but a short pilosulous or shorter strigulose, not lustrous hirsute vesture resembling that of the latter. An early collection from Bolivia (Santa Cruz, d’Orbigny) contributed to Bentham’s concept of a Cassia leptocarpa var. hirsuta; it has passed in northwestern Argentina as genuine C. hirsuta; and Chodat & Hassler identifed Paraguayan collections of it as either C. hirsuta, or C. pubescens, or a form of C. occidentalis, from which we here derive our varietal name. The variety’s perplexed history has arisen from the basic problem of distinguishing between C. hirsuta and C. leptocarpa at the specific level.

It is possible that var. puberula as here defined consists of two taxonomically discrete elements, one of the Andean piedmont and northwestern periphery of the Gran Chaco, the other confined or almost so to Paraguay. The Argentine plants have mostly 5-14-flowered racemes, the Paraguayan ones depauperate 2-5- flowered racemes like var. hirta, but there are already exceptions to this rule and we have yet to learn about the situation in central Gran Chaco, from which no material is at present available.

The synonymy of var. puberula goes back to surprisingly early days. We confidently refer here C. pubescens Jacqu., of which Bentham and subsequent botanists have had only hazy or erroneous notions, but we are at a loss to explain how it came into cultivation in Europe before the much commoner and more readily accessible var. hirta. Its early arrival in the Philippines, where Blanco saw it fully established as a roadside weed before 1837, is equally intriguing; one might have expected in its place var. hirta or even var. glaberrima as stowaways on the Acapulco-Manila trade route. In Mexico it was collected first by Sesse & Mocino (no. 1142, MA).