Monographs Details: Cassia viscosa Humb., Bonpl. & Kunth
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1978. Monographic studies in Cassia (Leguminosae, Caesalpinioideae). III. Sections Absus and Grimaldia. Mem. New York Bot. Gard. 30: 1-300.
Family:Caesalpiniaceae
Description:Species Description - Erect densely leafy shrubs and undershrubs (5-)6-20 dm, with 1-several stems either paniculately or thyrsoidally branching distally, except for the often glabrescent or glabrous upper lf- surface glutinously hispid or hispidulous throughout with pallid or yellowish setae up to 0.3-1.4 mm, often also minutely villosulous, the foliage either homomorphous or seasonally heteromor- phous, commonly ample at first becoming smaller upward and in or near the inflorescence, the lfts ± bicolored, usually paler beneath, the many short, usually few-fld racemes terminal to all distal branchlets or, with distal reduction of foliage, becoming at first axillary and rarely ultimately forming a leafless panicle. Stipules subulate, at first erect, in age commonly spreading or recurved, 0.6-2.5 mm, persistent but becoming dry and fragile. Lvs spreading, petiolate, the primary cauline ones mostly 3-10 cm, those of branchlets smaller, but mostly over 1.5 cm; pulvinus scarcely differentiated, sometimes discolored, ±0.8-2 mm; petiole (0.4-)0.5-30(-35) mm, at middle 0.4-0.9(-1) mm diam, narrowly obtusely winged ventrally, the groove almost closed; rachis 4-20 mm; lfts 2 pairs, the distal one mostly a little larger, displayed as in all Absoideae on linear or linear-elliptic pulvinule 0.6-1.7(-2) mm, in outline varying from asymmetrically ovate or broadly elliptic and obtuse to deltately acute-apiculate to obovate, inversely triangular, or obcordate and truncate to deeply emarginate, in all cases conspicuously mucronulate, those of primary cauline leaves 1-5 x (5-)7-30(-35) mm, at base usually cuneate distally and rounded to subcordate proximally, the entire margins at least at maturity revolute, the blades membranous or chartaceous, above green and often glutinously lustrous, varying from glabrous to thinly villosulous and setulose, beneath paler and duller, the slender midrib with (in larger lfts) 4-7 or (in smaller ones) mostly 3-4 pairs of secondary veins above immersed or almost so, beneath finely prominulous, the tertiary venulation either imperceptible or if raised then irregular, not forming a definite mesh. Racemes (solitary or rarely geminate) mostly (5-)8-25(-30)-fld, nearly always shortly pedunculate, either terminal to leafy branchlets and forming a pyramidal or round-topped panicle, or terminal to many short axillary branchlets of about the same length so as to form a leafy thyrse, sometimes by reduction of the secondary branchlets becoming axillary to major cauline leaves, the axis (2-)3-8(-12) cm, the 1-3 simultaneously expanded flowers raised about to level of succeeding buds; bracts spreading, lanceolate or subulate, 0.7-3 mm, persistent; pedicels permanently ascending, (7-) 11-20(-24) mm, bracteolate 1-11 mm below calyx; buds ovoid obtuse, glutinous and usually only thinly setulose; sepals submembranous, pallid, yellowish, or reddish, elliptic-oblanceolate to obovate- elliptic, 6-10(-11) x 2.2-4(-4.4) mm; petals yellow or orange-yellow, the 4 plane ones varying from broadly oblanceolate to obovate-cuneate, (10-) 12-20(-22) x 4-11(-13) mm, the dimidiately ovate coiled one either shorter or a little longer than the rest; ovary either villosulous or setulose; ovules 3-8. Pod 2-4 x 0.5-0.85(-0.9) cm, the valves always finely villosulous, often also finely or minutely setulose, less often coarsely setose; seeds oblong-obovoid, 3.2-4.5(-5) x 1.9-2.8 mm, the moderately lustrous testa atrocastaneous or black, faintly (sometimes almost imperceptibly) lineolate rarely finely pitted all over.

Discussion:

Phenotypic variation in the widely but discontinuously dispersed C. viscosa follows two concurrent, sometimes mutually antagonistic modes, one genetic, the other seasonal. The branching patterns of the panicle, the outline and potential amplitude of the leaflets, and the potential size of the flower appear to be under genetic control, but the actual state of inflorescence development and the actual size of leaf and flower in the individual plant vary with its age, the panicle becoming more elaborate during the course of an ordinarily prolonged annual growth-cycle while the leaf and flower dwindle. The two types of variation become separately visible when material of different ages from the same general area can be assembled, but they make a precise definition of intraspecific taxa very difficult and a reliable key to them unattainable. It seems useful nevertheless to distinguish within C. viscosa three major categories: a) var. viscosa, centered on the eastern Cordillera of Colombia, with outlying populations in lowland eastern Venezuela (Gran Sabana, Bolivar) and along the Pacific slope of Mexico between Guerrero and Sinaloa, this characterized by relatively ample primary foliage, seldom obcordate leaflets, a paniculate inflorescence of large early flowers, and a hispid pod; b) a var. paraguayensis, dispersed around the southwestern margin of the Brazilian planalto and extending into Paraguay, morphologically similar to var. viscosa except for the softly villosulous, at best minutely setulose pod; and c) a polymorphic var. major, extending from Mt. Roraima and the Pakaraima Mts., eastward through the interior Guianas, Para, south and southeastward to Ceara, s.-w. Minas Gerais, and n. Mato Grosso, characterized by a more thyrsiform mature panicle of mostly smaller flowers combined with small leaves and prevailing obcordate or inversely triangular leaflets. While this type of leaflet is ordinarily the most arresting single feature of var. major it is not, in itself alone, taxonomically reliable, as Amshoff (1939, p. 23) has pointed out in reducing to synonymy C. viscosa var. acuta and Grimaldia columbiana, originally segregated on the basis of acute leaflets. The type of var. acuta, however, has the thyrsiform inflorescence, small leaflets and minutely setulose pod of sympatric lower Amazonian C. viscosa var. mayor, while that of G. columbiana has the paniculate inflorescence, larger flowers and hispid pod of sympatric cordilleran var. viscosa. They represent parallel modifications of a type common within what we define as var. viscosa, but almost unique in var. major, which Amshoff seems to have regarded as the more typical expression of C. viscosa sens, lat., certainly the one prevalent in the Guianas, Para, and eastern Brazil.

Key to the varieties of C. viscosa

1. Primary cauline lvs relatively ample and long-petiolate, the petiole up to 1.5-3.5 cm, the rachis to 0.7-2 cm, the longer lfts 2.5-5 cm, mostly ovate-elliptic, obtuse or acute, rarely emarginate.

2. Plants of Colombia and adjoining Venezuela (Magdalena Valley and llanos along e. base of Cordillera Oriental) and disjunctly both in Mexico and (transitional to var. major) on the Gran Sabana in Venezuelan Guayana; pod hispid with setae up to 0.6-1.5(-2) mm.

156a. var. viscosa

2. Plants of Paraguay and adjoining Brazil (s. Mato Grosso, w. Sao Paulo, and Triangulo Mineiro); pod finely villosulous, the setules (if present) at most 0.5 mm, scarcely longer than the villi.

156b. var. paraguayensis

1. Primary cauline lvs shorter and more shortly petioled, the petiole 5-21 mm, the rachis 4-12 mm, the larger lfts 1-2.5(-3) cm, mostly obcordate or inversely triangular, only exceptionally elliptic and acute; lower Amazonian Brazil, n. into the Guianas, s. and s.-w. into Ceara, s.-centr. and s.-w. Minas Gerais, Goias, and n.-e. Mato Grosso.

156c. var. major

Distribution:Venezuela South America| Colombia South America| Bolívar Venezuela South America| Mexico North America| Sinaloa Mexico North America| Guerrero Mexico North America| Brazil South America| Mato Grosso Brazil South America| Ceará Brazil South America| Pará Brazil South America|

Narratives:Cassia viscosa