Senna macrophylla (Kunth) 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.

Family

Caesalpiniaceae

Scientific Name

Senna macrophylla (Kunth) H.S.Irwin & Barneby

Type

Typus infra sub var. macrophylla indicatur.

Synonyms

Cassia macrophylla Kunth

Description

Species Description - Shrubs and treelets, the latter sometimes sarmentose when crowded, rarely precociously flowering as stout herbs, normally terrestrial but occasionally encountered as epiphyte in crotch of forest-tree, at anthesis (1-) 1.5-9 m, the stiff or pliant, terete or obtusangulate branchlets with lf-stalks, axes of inflorescence and lower face (at least along major veins) of lfts densely to very sparsely strigulose or pilosulous with forwardly subappressed, incurved or spreading hairs up to 0.1 -0.6(- 1.2) mm, the ample, thin-textured subconcolorous, intricately reticulate lft-blades always glabrous above, the short inflorescences either axillary or cauliflorous, then often several in a vertical file. Stipules caducous (hence poorly known), varying from slenderly setiform to amply foliaceous, 0.45-12 x 0.02-5 cm, when foliaceous resembling the lower pair of lfts but smaller. Lvs 1.5-7.5 dm; petiole including little swollen but deeply wrinkled pulvinus 1.5-28 cm, at middle 1.2-4.5 mm diam, openly, very shallowly sulcate ventrally; rachis 2-12 cm, a little longer to much shorter than petiole; gland 1 sessile or almost so between proximal pair, ovate- or lance-linguiform obtuse glabrous 2-5(-6) mm tall; pulvinules 2.5-9(-10) mm; distal pair of lfts subsymmetrically ovate, ovate-elliptic or elliptic, shortly acuminate or caudate, 10-44 x 4-18(-24) cm, 1.8-2.7 times as long as wide, at base cuneate to rounded or shallowly cordate on both sides or sometimes cordate only on proximal one, the margin plane or obscurely revolute, the slender straight or slightly incurved midrib above immersed or shallowly depressed, sharply cariniform beneath, the 9-18 major camptodrome (with random intercalary) secondary veins and complex reticulation raised on both faces, the ultimate defined areoles of the reticulum <0.5 mm diam. Axis of compound inflorescence (leafless branchlet) 0-1.5 cm, when 0 the raceme solitary, axillary or shortly supra-axillary; peduncle 0-4 cm; racemes (4-)7-25(-30)-fld, at anthesis rather dense, often subcorymbose, the axis becoming 0.5-5.5 cm; bracts (early caducous, seldom seen) lance- or oblance-elliptic membranous-margined 1.7-3.5 mm; pedicels at full anthesis very slender pliant 1.5-4.7(-6.5) cm, much thickened but little longer in fruit; buds globose when young, glabrous or thinly pilosulous, opening before maturation of androecium; sepals little graduated, when dry prominently pallid-veined against a dull purplish- or grayish-brown field, in outline ovate, elliptic-ovate or -obovate, or oblong- oblanceolate, always obtuse, the outer ones 6.5-10(-11) mm, all prominently 5-7-veined from base, the veins arborescently branched and the branches anastomosing with their neighbors; petals homomorphic or the adaxial one slightly broader than the rest, pale yellow, when dry pallid (rarely golden) dark-veined, puberulent dorsally especially along prominulous veins, beyond the slender claw oblong-oblanceolate to obovate, obtuse or emarginate, (11-) 12-25(-29, reportedly "35") mm long; functional androecium 7-merous, the filaments puberulent or glabrate, little unequal 1.7-3.7 mm; anthers glabrous 4.5-7.5 mm, of similar size but the 3 abaxial sometimes a little shorter and often more strongly incurved, those of 4 median stamens with abruptly divaricate 2-porose beak 0.4-0.8 mm, those of 3 abaxial ones with sigmoidally porrect beak 0.8-1.8 mm; ovary densely pilosulous, thinly pilosulous or glabrous, the style moderately dilated, at oblique tip 0.7-1.2 mm diam, the orifice (0.3-)0.45-l mm diam; ovules 152-250. Pod (of var. gigantifolia, that of var. macrophylla unknown) pendulous, the stout stipe 4-10 mm, the linear body (10-) 15-28 x 0.75-1 cm, abruptly contracted at both ends, somewhat dorsoventrally compressed and sulcate along the sutures, a trifle constricted between the seeds, the green valves becoming thin-textured and nigrescent, the ventral suture 1-2 mm wide, the cavity divided lengthwise by a narrow pithy septum extending from suture to suture; dehiscence unknown, perhaps irregular by rotting; seeds biseriate, turned broadside to the septa, enveloped in thin blackish pulp, narrowly oblong-ellipsoid 3.8-5.3 mm, the testa dull black, exareolate.

Variety Key - Key to the Varieties of S. macrophylla 1. Lvs extremely large, the larger cauline ones 3-7.5 dm, with petiole (6-)7-28 and rachis 5.5-12 cm, the blades of the distal pair of lfts 18-37 cm; Orinoco and Amazon basins, in Venezuela extending w. and n. to Cordilleras de Merida (Orinoco slope) and Costanera. 17a. var. gigantifolia (p. 139). 1. Lvs of moderate size, 1.5-3.5(-4) dm, with petiole 1.5-6(-8.5) and rachis 2-6.5(-9) cm, the blades of the distal pair of lfts 10-23(-26) cm; inter-Andean valleys of centr. and n. Colombia, thence extending to the e. slope of Cordillera Oriental in Meta and to the Caribbean slope of Cordillera de Merida in Venezuela. 17b. var. macrophylla (p. 140).

Discussion

A species instantly recognized at anthesis by its prominently venulose, usually glabrous sepals, but variable in other ways, especially in pubescence, in position and elaboration of the inflorescence, in size of leaves and flowers, in proportion of sepals to petals, and in stature as determined by environment and age of the indivdual plant. In fruit it may be distinguished from sympatric relatives by the intricate reticulation of the leaflet blades combined (at least in the case of var. gigantifolia) with a dorsoventrally compressed pod with narrow sutures. The populations found in the inter-Andean valleys of northern and central Colombia (=our var. macrophylla) have consistently setiform stipules, almost always relatively small, short-petioled leaves consistently pilosulous beneath, and are not known to bear their consistently smallish flowers otherwise than in simple, solitary racemes axillary to living leaves. The populations within and around the margins of the upper Orinoco and Amazon basins differ in the almost always longer petioles and ampler, often truly immense leaflets, but are perplexingly variable in other characters. The stipules vary from setiform to amply foliaceous, sometimes so large as to resemble a pair of basal leaflets; the vesture varies from rufescently pilose to minutely strigulose; the racemes may be either axillary and solitary as in var. macrophylla or borne on condensed leafless branchlets, these either arising from new or from old wood, in the latter case often several together in a vertical supra-axillary file; and the petals vary from 1.5 to 3 times as long as the sepals. We have failed to detect among these often striking individual but apparently random variables any pattern of correlation and we are ultimately able to distinguish the Colombian and marginally Venezuelan and Panamanian var. macrophylla from its Hylaean counterpart only by the usually neater foliage. In consequence we return to Bentham’s concept of Cassia macrophylla sensu lato, recognizing a polymorphic C. gigantifolia as a poorly defined variety. Of recent segregates, Chamaefistula hazenii is merely a youthful var. macrophylla, flowering precociously as a stout herb or weakly woody shrub; whereas Ch. gigantifolia (sens, str.) and Ch. barbinervis represent the strigulose and pilose states, respectively, of our var. gigantifolia, sens, ampliat.