Senna pendula var. scandens (Benth.) H.S.Irwin & Barneby
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Authors
Howard S. Irwin, Rupert C. Barneby
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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.
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Family
Caesalpiniaceae
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Scientific Name
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Synonyms
Cassia laevigata var. scandens Benth., Cassia floribunda var. scandens (Benth.) Lass.
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Description
Variety Description - Weak sarmentose shrubs up to 3(-?) m, the membranous lfts puberulent along midrib above, thinly pilosulous beneath with straight ascending hairs up to ±0.60.8 mm; a gland between all pairs of lfts or all but the distal one; lfts 3 or 4 pairs, ovate or lance-ovate from inequilateral base, the distal pair ±3.5-5.5 x 1.5-2 cm, the secondary camptodrome veins ±8-10 on each side of midrib, tertiary venulation faint and irregular; longest sepal 8-11.5 mm; longest petal 13-15 mm; blade of staminodes trapeziform ±2.5-3.5 x 2 mm; 2 long abaxial filaments 10-11.5 mm, their anther 8-9 x 1-1.3 mm, its beak weakly differentiated; ovary glabrous; style ±4-5.5 mm; ovules (1 count) ±88; body of pod (scarcely known) apparently only 7—9 cm long subterete, the seeds 2-seriate.—Collections: 4. [Key: "Lfts ovate or ovate-elli[tic, broadest well below middle; local in Amazonian Peru (San Martin)."]
Distribution and Ecology - Forest margins, shores and steep grassy slopes along rivers, 200-1100 m, apparently local, known only from the valleys of Rio Huallaga and its tributary Rio Mayo in San Martin (prov. Moyobamba, Lamas and San Martin), Peru.—Fl. VI- VII, and to be expected at other seasons.
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Discussion
The var. scandens was subordinated with doubt by Bentham and definitively by Lasseigne to the species treated herein as Senna septemtrionalis. This species was thought at the time to be native both in North and South America, so that the budding off of a local variant in trans-Andean Peru occasioned little surprise. We have developed the contrary view that S. septemtrionalis is only adventive in equatorial latitudes and native only in Mexico and Central America, and consider a direct genetic connection between it and var. scandens highly improbable. Morphologically var. scandens resembles the Hylaean forms of S. pendula in everything but outline of the leaflets, which are broader below, not above the middle. They are, however, asymmetric at base as in S. pendula, not subequi- lateral as in S. septemtrionalis, while the small known range of dispersal fits into that of S. pendula sens. lat. like a chip missing from a mosaic. We suspect that var. scandens is most closely related to var. praeandina which replaces it in the same environment immediately to the southward. Together with the ovate leaflets, unknown otherwise in S. pendula, the trapeziform staminodes and relatively few-ovulate and short pod form a strong differential syndrome.
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Distribution
San Martín Peru South America|