Senna papillosa

Title

Senna papillosa

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna papillosa (Britton & Rose) H.S.Irwin & Barneby

Description

13.  Senna papillosa (Britton & Rose) Irwin & Barneby, comb. nov. Chamaefistula papillosa Britton & Rose, N. Amer. Fl. 23(4): 237. 1930.—Typus infra sub var. papillosa indicatur.

Weak shrubs and trees, sarmentose and vinelike when crowded, flowering often when only 1.5-3 m but when adult potentially attaining a stature of 9(-10) m and trunk diam of 1.5 dm, strigulose-pilosulous with fine straight and appressed or forwardly incumbent, less often with erect-incurved, whitish or (distally) faintly lutescent hairs up to 0.1-0.35 mm, the hornotinous branchlets terete striate or bluntly angled by ribs descending from the stipules, the foliage bicolored, the thinly chartaceous lfts dull or sublustrous olivaceous above, paler beneath, the faces equally pubescent or the upper (or both) only thinly so along principal nerves, the solitary, less often geminate racemes all or partly leafy-bracteate or sometimes all exserted from foliage, the primary axis of the commonly pendulous, narrowly thyrsiform inflorescence at first or in age abruptly flexuous or zigzag.

Stipules caducous, mostly falling before maturity of associated lf, linear-oblanceolate acute 4.5-14 x 0.6-2 mm.

Lvs below (and often through part or all of) the inflorescence 13-27(-32) cm; petiole including pulvinus (1.2-) 1.6-4.5(-5) cm, at middle (l-)1.2-2.4(-3) mm diam, the open shallow ventral groove widened upward toward the gland; rachis

1.5-4.5(-5) cm, varying from little longer to little shorter than petiole; gland 1 sessile or subsessile between proximal pair of lfts, in profile 1.5-5(-6) mm tall, the glabrous body varying from stoutly ovoid to lance-ellipsoid, obtuse or acute, 0.5-2.6 mm diam; pulvinules (2.5-)3-7 mm; distal pair of lfts very obliquely elliptic, obovate- or ovate-elliptic acuminate (8.5-) 10-23 x (3.2-)3.6-9.5 cm, 2-3(-3.8) times as long as wide, at base broadly cuneate to rounded on proximal and cuneate on distal side, the margin (adult) plane or almost so, the strongly displaced, forwardly incurved midrib with ±(7-)8-13 pairs of major camptodrome and usually several intercalary secondary veins together with connecting tertiary and subsequent reticular venulation finely prominulous above and equally or more sharply so beneath, but the ultimate well-defined mesh variable, the smallest areoles either much > or < 1 mm diam.

Racemes densely (4-)7-30(-50)-fld, the axis including the short, sometimes subobsolete peduncle becoming (1-) 1.5-9(- 14) cm; bracts very early dry caducous, ovate or lanceolate 1.2-3 mm; pedicels mostly 2-4.2, less comonly only

1.2-2 cm; young fl-buds globose, strigulose; sepals either firm throughout or (when broad) firm with membranous margins, only a little graduated in length, varying from broadly obovate very obtuse to obovate and deltately subacute or elliptic-oblong-oblanceolate and obtuse, the longest 3-10 mm, all at anthesis obscurely venose but in age becoming more prominently 3-6-veined from base; petals (of ser. Bacillares) puberulent dorsally or on both faces, varying in outline from oblong-oblanceolate to broadly obovate, the longest (of fully expanded fls) 7.5-23 mm; functional stamens 7, the filaments puberulent, of 4 median stamens filiform or slightly thickened upward 1.4-3.8 mm, of 3 abaxial ones (1.5-)2-5 mm, the anthers puberulent in the grooves, of 4 median stamens gently curved 4-7(-7.5) mm with divaricate 2-porose beak 0.4-0.7 mm, of 3 abaxial ones lunately incurved 3.6-5.5(-6) mm with porrect beak (0.9-)l-2 mm, its orifice 1-porose or divided by a filiform septum; ovary densely strigulose or pilosulous with either whitish or lutescent hairs; style little inflated until after fertilization, at anthesis 0.6-1 mm diam just below the stigmatic orifice, this 0.4-0.7 mm diam; ovules 140-220(-256).

Pod pendulous stipitate, the stipe 5-20 mm, the straight or gently decurved body terete or obscurely compressed-quadrangular (1.5-)2-4(-4.7) dm long, 7- 10(- 11) mm diam, contracted into a persistent (but fragile, often broken) stylar beak 5-17 mm, the sutures not or scarcely differentiated externally, the valves dull green ripening brown or reddish-brown, very densely coarsely granular-papillate overall, finally dehiscent through ventral suture and explanate to expose the biseriate seeds embedded, broadside to the septa, in thin slimy foetid pulp; seeds ellipsoid or subreniform-ellipsoid 3.5-5.7 x 2-3 mm, the atrocastaneous lustrous testa smooth or remotely pitted, exareolate.

The species described above as S. papillosa is the same for which Bentham (1871) provisionally but mistakenly took up the name Cassia inaequilatera Balbis, a species safely and certainly distinguished from all forms of S. fruticosa, S. bacillaris, S. oxyphylla and S. dariensis by the long narrow pipelike, ultimately dehiscent pod coarsely granular-papillate overall and at the same time lacking externally differentiated sutures. In kindred species with terete pod the valves, except where venulose or remotely resinous-verruculose, are perfectly smooth and at maturity often glossy, and the sutures form conspicuous bands down the length of the dorsal and ventral faces, bands emphasized in S. bacillaris and S. oxyphylla by thickened borders. The pod of S. fruticosa, which lacks such borders, is terete like that of S. papillosa but at once much shorter and broader, while that of S. dariensis, though equally long, is at once narrower and strongly compressed laterally, with coarse salient sutures and seeds marshalled into a single row. The seeds of S. papillosa differ from those of S. fruticosa and S. bacillaris in their ellipsoid form and lack of areole, but except for the generally narrower outline are scarcely different from those of S. oxyphylla.

While instantly recognized in the fruiting stage, S. papillosa at anthesis cannot, as Bentham realized, be readily distinguished from true S. bacillaris or, we must add, from all forms of S. oxyphylla, S. fruticosa and S. dariensis, with each of which it shares part of its range. The problem is aggravated by the fact that the inflorescence, which may be either leafy-bracteate throughout or leafless and exserted, and the individual flower, which varies considerably in length and amplitude and lacks any distinctive feature in the androecium, both tend to resemble in form those of the immediately sympatric relative: in Veracruz and Oaxaca S. fruticosa; in middle Central America S. bacillaris and S. dariensis; in northern South America S. oxyphylla. In practice we have identified as S. papillosa those Mexican flowering specimens which appear to differ from sympatric S. fruticosa by appressed leaf-pubescence and sharply short-acuminate leaflets together with at least 140 (not ±80-100) ovules; and those large-flowered Central American ones with proximal leaflets not very highly asymmetric and sepals relatively firm and narrow as compared with S. bacillaris. But recognizing the likelihood of error we have taken care to formulate the statement of range on evidence of fruiting specimens alone. These establish for S. papillosa a certain northern limit at Mi- santla on the Gulf slope in Mexico near 20°N and a southern one on Sa. de Maca- rena in trans-Andine Colombia at 3°N. The apparent absence of S. papillosa from east-central Panama may be explained, perhaps, by a fortuitous lack of fruiting material from the area.

At its southern limit S. papillosa is represented by a series of populations notable for many geminate racemes in the inflorescence, a tiny calyx, and exceptionally short-pedicelled small flowers. This, already described as Chamaefistula angusta, deserves varietal status. The four Brittonian chamaefistulas listed in the synonymy of var. papillosa were described without any diagnostic prognosis of substance and can be dismissed without further ceremony.