Senna pallida var. gaumeri (Britton & Rose) 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 2: 455-918.

Family

Caesalpiniaceae

Scientific Name

Senna pallida var. gaumeri (Britton & Rose) H.S.Irwin & Barneby

Type

Holotypus, collected at Izamal, date unknown, NY! = NY Neg. 9395; isotypi, F, US, W!-Cassia gaumeri (Britton & Rose) Lundell, Carnegie Inst. Publ. 478: 212. 1937.

Synonyms

Peiranisia gaumeri Britton & Rose, Cassia gaumeri (Britton & Rose) Lundell, Peiranisia yucatensis Britton & Rose, Cassia yucatensis (Britton & Rose) Lundell

Description

Variety Description - Shrubs 1-3 m with stiffly ascending or virgate pallid terete annotinous and prominently ribbed hornotinous branchlets, seasonally dimorphic in aspect due to replacement during drought of longer lvs by smaller-lfd axillary brachyblasts, varying from glabrous below the strigulose ovary to densely pilosulous everywhere except for glabrous sepals with spreading or incurved-ascending hairs up to 0.2-0.6 mm, the foliage moderately bicolored, the lfts often distinctly resinous- dotted above, paler beneath, the 2-fld racemes borne on either inhibited or shortly developed but then leafy brachyblasts, surpassing the lvs of these but surpassed by the major cauline ones. Stipules of primary lvs subulate-setiform 1.5-6 x 0.2-0.5 mm, those of brachyblasts shorter and more persistent. Primary cauline lvs (absent from most fruiting and some flowering spms) 4-7(-10) cm; petiole (6-)9-16 mm, 0.4-0.7 mm diam, 1.2-2 times as long as first interfoliolar segment of lf-stalk; gland at proximal (exceptionally also at second) pair, stipitate or subsessile (1-)1.5-2.5 x 0.3-0.7 mm; lfts 4-6 pairs strongly accrescent upward, obovate or cuneate-obovate obtuse or deltately acute mucronulate, the distal (largest) pair 1-2(-2.8) x 0.6-1.1 cm, 1.7-2.5 times as long as wide, the midrib and 4-6 pairs of camptodrome (with random intercalary) secondary veins immersed and imperceptible above, faintly prominulous beneath, tertiary venulation not developed; lfts of brachyblasts mostly (2-)3-4 pairs, smaller. Peduncles 4-16 mm; pedicels 8-18 mm; long sepals (4.5-)5-7 mm; long petals 1-5 mm; filaments glabrous free to base, those of 4 median stamens 1-1.5 mm, of 3 abaxial ones 2-4.7 mm, the anthers of 4 median stamens 2.8-4.5 mm abruptly truncate the very short lateral beak of all, or of at least the 2 longer ones opening by parallel slits, these sometimes confluent into a U-shaped slit in one or two of the shorter ones, the anthers of 3 abaxial stamens 3-6.5 mm, their beak 1.3-2 mm; style 0.9-1.3 mm. Stipe of pod (3-)4-7 mm, the body 5.5-8.5 cm x (4.5-)5-6.5 mm, the septa 2.5-3 mm apart; seeds broadly obovate-suborbicular or paddle-shaped in lateral view, 2.9-3.5 x 2.4-3.5 mm, the areole 0.5-0.7 x 0.3-0.5 mm.-Collections: 16. [Key: "Appendage terminal of lf-stalk subulate or setiform, not modified and dilated into a gland; range of whole species. Continental N. and S. America and Lesser Antilles, s. Windward Is. and Swan Is. in s. Caribbean; anthers nearly always stouter (1.2-)1.3-2 mm diam, abruptly truncate at apex and the tubules there commonly umbonate at the angle opposed to the laterally divaricate, often slightly infra-terminal beak, if whole anther less than 1.25 mm diam and umbo pronounced. Reticulate tertiary venulation imperceptible or almost so on both faces of lfts, these superficially either penninerved or veinless. Lfts or larger primary cauline lvs 2-8(-9) pairs, perceptibly and usually conspicuously accrescent distally, the terminal pair longest; areole of seeds 0.4-0.9 mm in greatest diam. Scattered over s. Mexico and Guatemala. Plants of Yucatan Peninsula, Mexico. Lfts of primary cauline lvs 4-6 pairs, of brachyblast lvs (2-)3-4 pairs; seeds smooth; Campeche, Yucatan and Quintana Roo, relatively widespread and common."]

Distribution and Ecology - Thickets and glades in the drought-deciduous woodland, becoming abundant in disturbed scrub and brush, below 100 m, widespread over the n.-w. half of Yucatan Peninsula, from coastal Campeche (Chapoton) n.-e. to e. Yucatan (Tizimin) and n. Quintana Roo.-Fl. I-VI, then sparingly through the year.

Discussion

Peiranisia yucatensis and P. gaumeri, here evaluated as more and less pubescent aspects of S. pallida var. gaumeri, were characterized by Britton & Rose (1930, p. 259, in key) as having only 3-4 pairs of leaflets not over 1 cm long. The typi of both species were collected in the drought phase and have all complete leaves and flowers issuing from axillary brachyblasts, the leaves therefore much smaller than the primary cauline ones, all shed except in part of P. gaumeri, where long but naked leaf-stalks with up to 6 pairs of scars remain to tell the tale. Even though they were originally segregated from P. biflora sensu Britton & Rose (which covered our S. pallida var. pallida and var. bahamensis) for the wrong reason, these xeromorphic populations from Yucatan Peninsula, of which we now have many examples of the more amply leafy, wet-season phase, seem genuinely to differ from var. pallida in the simpler venation of the leaflets, markedly so from the races of var. pallida native to Veracruz shortly to the west. In other respects, especially in the relatively short and wide pod elevated over the seeds as a simple mound or very obscure pyramid and in the resinous-dotted leaflets, var. gaumeri simulates var. bahamensis, although retaining the stout anthers of var. pallida. But the erratic dehiscence of some of these anthers by one U-shaped rather than two discrete parallel slits suggests a line of affinity leading toward S. angustisiliqua distantly allopatric on the Greater Antilles and in northern South America.

Distribution

Yucatán Mexico North America| Quintana Roo Mexico North America| Campeche Mexico North America|