Senna pallida var. trichocraspedon

  • Title

    Senna pallida var. trichocraspedon

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna pallida var. trichocraspedon (Sandwith) H.S.Irwin & Barneby

  • Description

    177r. Senna pallida (Vahl) var. trichocraspedon (Sandwith) Irwin & Barneby, stat. nov. Cassia trichocraspedon Sandwith, Kew Bull. 1936: 6. 1936.- "MEXICO. State of Mexico: District of Temascaltepec; Ypericones . . . fl. and fr. Feb. 1934, Hinton 5582 . . -Holotypus, K! = NY Neg. 1426; isotypi, F, NY! paratypi, Hinton 355, 2972, 5742, all F, K, and all but 355, NY!

    Cassia tortuosa Smith & Schubert, Contrib. Gray Herb., n. ser. 127: 21, t. 1, fig. 16-18. 1939.- "MEXICO: Mexico: distr. Temascaltepec, Nanchititla . . . June 11, 1934, Hinton 6144 . . -Holotypus, GH! isotypi, F, MEXU, NY, US!Slender, ultimately arborescent shrubs at anthesis 1-5 m with terete or faintly ribbed, often abruptly flexuous but stiff branches, either pilosulous throughout with spreading or spreading-incurved hairs up to 0.3-1 mm, the lfts then pubescent on both faces but more densely so beneath, or only the young stems and lf- stalks pilosulous and the lfts then glabrous ciliolate, the inflorescence formed of 1-several, mostly 2-fld racemes pseudofasciculate or shortly racemose on leafless brachyblasts axillary to coeval or lately fallen lvs, some rarely terminal to branchlets.

    Stipules setiform 1.5-6 mm.

    Major lvs 7-12.5(-14) cm; petiole (7-) 10-20 mm; rachis (3-)4-8.5 cm; gland between or immediately above first pair of lfts stipitate, including glabrous or hispidulous stipe 3-4 mm, the lance-elliptic body 0.55-0.7 mm diam; sometimes a similar gland between second pair, and the seta similarly modified but more slender; lfts (6-)7-10(-11) pairs, commonly but not always heteromorphic, those of lvs low on the branchlets often proportionately broader and more obtuse than the rest, the majority lance- or oblong-elliptic acute, some oblong-obovate sub- obtuse, always accrescent upward along rachis, the distal pair (2-)2.5-4.5 x 0.6-1.2 cm, ±2-3 times as long as wide, the margins strongly revolute at maturity, the centric midrib with 6-10 pairs of major camptodrome secondary nerves finely prominulous above, sharply and more strongly so beneath, tertiary reticulation 0 or weak and irregular.

    Peduncles (3-)8-20 mm; pedicels 12-24 mm; long sepals ±6-8 mm; long petals up to 20-28 mm; androecium glabrous, the filaments of 4 median stamens 1.1-1.6 mm, of 3 abaxial ones 2.5-5 mm, the anthers of 4 median stamens 4-5 mm, of 3 abaxial ones 5-7, their beak 2-2.8 mm; ovary ciliate or ciliolate along sutures, glabrous or almost so laterally; style 1.2-1.5 mm; ovules 26-34.

    Stipe of pod 4.5-9 mm, the body 7.5-13 x 0.6-0.85 cm, the papery valves nigrescent glabrous, the sutures either permanently pilosulous-ciliolate or gla- brescent; seeds 3.4-4.8 x 3-3.7 mm, the areole oblong-elliptic 1-1.7 x 0.5-0.9 mm.-Collections: 9.

    Oak woods and brushy hillsides in the oak-pine belt, ±1400-1700 m, local in the s. and s.-w. foothills of Volcan Toluca in mun. Temascaltepec, Amatepec, and Almoloya de Alquisiras, Mexico.-Fl. XII-III.

    In the protologue of C. trichocraspedon Sandwith emphasized as diagnostic features the copious pubescence of the leaves and especially the fringe of hairs persistent along the pod sutures, but he recognized the relationship to Peiranisia palmeri (our S. pallida var. palmeri), very similar in the pod although different in the glabrate, broader and blunter, less venulose leaflets. The pubescence of the typus and several paratypi of C. trichocraspedon, all of which are derived from two localities (Ypericones and Telpintla) about 20 km apart, is indeed peculiar in the group, but the typus of C. tortuosa, which has the same glandiform seta and broad pod as C. trichocraspedon, and which was described from a station immediately contiguous to Cerro de Ypericones, has glabrate ciliolate foliage and only residual cilia along the sutures of the pod. We feel certain that these two are merely aspects of one taxon, the diagnostic value of pubescence being, as elsewhere in ser. Rostratae, illusory. Collectively C. trichocraspedon and C. tortuosa differ significantly from other Mexican forms of S. pallida only in the terminal gland of the leaf-stalk, analogous to that of Costa Rican var. cordillerae, which differs chiefly in its thin-textured, very markedly bicolored, less venulose leaflets and those characters brought out in our varietal key. The highly irregular corolla, thought by Smith & Schubert to distinguish C. tortuosa from other Interglandulosae, is actually, to the contrary, characteristic of the series and in no detail different from the corolla of sympatric C. trichocraspedon.