Senna araucarietorum 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
-
Type
Holotypus, NY; isotypi, BR, US!
-
Description
Species Description - Amply leafy shrubs with terete green subfistular hornotinous branchlets at anthesis 1-3 m (not known to be arborescent), in general aspect resembling S. septemtrionalis, glabrous except for minutely puberulent pulvinules, ovary, or sometimes remotely ciliolate lfts or sepals, the thin-textured foliage bicolored, when dry rich dark green and sublustrous above, paler dull beneath, the short racemes of small fls lateral and much surpassed by the subtending lf, not known to form a terminal panicle. Stipules erect submembranous pallid or greenish, narrowly lance-acuminate or linear acute 2.5-6 x 0.6-1 mm, caducous before maturity of the associated lf, lacking from many spms. Lvs 12-30 cm; petiole including wrinkled discolored pulvinus (3.5-)4.5-9 cm, at middle 0.9-1.6 mm diam, openly shallowly sulcate ventrally; rachis (2.5-)4-9 cm, the longest interfoliolar segment (2.2-)2.5-4.5 cm; gland between all pairs or all but the distal pair of lfts, subsessile or shortly stipitate, the proximal one 1.5-2 mm tall, the plumply ovoid apiculate or lance-fusiform body 0.6-1 mm diam, the more distal glands either similar or smaller; pulvinules 2-3 mm, when dry livid and wrinkled; lfts 2-3(-4) pairs, accrescent distally, the distal pair narrowly ovate- to broadly lance-acuminate (5.5-)6-12 x 2-3.5 cm, (2.5-)2.6-3.6 times as long as wide, at base subequilaterally rounded or cuneate, the pallid membranous margin plane, the midrib beneath pallid cariniform, above immersed or nearly so, the 12-18 pairs of slender camptodrome secondary veins with slender tertiary and reticular venules all ± prominulous on both faces but more sharply so beneath. Racemes shortly, at first subumbellately 6-13-fld, the axis together with slender peduncle 2.5-6 cm, shorter than or rarely equalling the associated petiole; bracts subulate 1.5-4.5 mm, like stipules in shape and texture, early caducous; mature fl and fr pedicels 7-15 mm; sepals yellowish or fuscous-tinged, well graduated, the ovate outermost one 3-3.5 mm, the obovate cucullate innermost one 5.5-9 mm; petals essentially of S. septemtrionalis, the vexillar one 11-14 mm; androecium glabrous, the blade of staminodes obovate 1-1.3 x 1 mm, the filaments of 4 median stamens 1-2 mm, of the centric abaxial one 2-2.5 mm, of the 2 latero-abaxial ones (4.5-)5-7.5 mm, the anthers brownish, of 4 median stamens lance- oblong 3.2-4 x 0.8-1.2 mm, of the centric abaxial one 4-4.8 x 0.6-1 (either obviously sterile or substantially narrower than its neighbors), those of 2 long stamens lunately lanceolate from obtuse base 4.8-5.6 x 1.1-1.5 mm, obscurely strangulate 0.4-0.5 mm below the symmetrically truncate orifice, there 0.7-0.8 mm diam, dehiscent by U-shaped slit; ovary minutely puberulent laterally; style 2.8-3.4 x 0.25-0.4 mm, slightly incurved distally; ovules 28-42. Pod obliquely geotropic, the stipe 3-4.5 mm, the linear straight subcylindric but when fresh apparently slightly compressed body 7-10.5 x 0.5-0.75 cm, the smooth green, when ripe papery brunnescent or fuscous valves narrowly margined along the sutures, the 1-seriate seed-locules not or scarcely pulpy, occupying the width of the pod’s cavity, 1.6-2.4 mm long; seeds turned with broader faces to the septa, plumply compressed-obovoid or -spheroid 3.8-4.8 x 2.8-4.2 mm, the smooth brown testa highly lustrous, exareolate.—Collections: 16.
Distribution and Ecology - Thickets, clearings and margins of secondary woodland, often associated with Parana pine, ±800-1400 m, hill-country w. of the coastal serra in Parana and Santa Catarina, Brazil, and adjacent Misiones, Argentina, occupying a range interposed between those of S. hilariana and S. corymbosa to the s.-w. and that of S. tropica to the n.-e.—Fl. mostly X-III, perhaps throughout the year.
-
Discussion
This somewhat cryptic species, along with related S. tropica, has been mistaken in herbaria for Cassia laevigata (=our Senna septemtrionalis) which may possibly occur in its range as a weed, although native in remotely distant Mexico and Central America. Senna araucarietorum resembles S. septemtrionalis in its ample leaves and in the ovate-acuminate outline of its leaflets, but these are on average fewer, only 2-3 rather than 3-5 pairs, and the pod is quite different, resembling that of S. corymbosa in its slender girth and in the single stack of no more than 42, commonly less than 40 (as opposed to 50-80 biseriate) seeds housed in pulpless locules. The range of S. araucarietorum lies to the west of the Atlantic divide southwestward from the head of Rio Iguaçu in northeastern Parana. Northeastward from this point, but always on the Atlantic slope, it is replaced by the habitally similar S. tropica which differs like S. septemtrionalis in the multi-ovulate fruit and biseriate seeds, but can be separated instantly at anthesis by the peculiar development of the umbos at the tip of the long anthers.
-
Distribution
Paraná Brazil South America| Santa Catarina Brazil South America| Misiones Argentina South America|