Senna pallida var. quiedondilla

Title

Senna pallida var. quiedondilla

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna pallida var. quiedondilla (Micheli) H.S.Irwin & Barneby

Description

177k. Senna pallida (Vahl) var. quiedondilla (Micheli) Irwin & Barneby, stat. nov. Cassia quiedondilla Micheli, Mem. Soc. Phys. Sci. Nat. Geneve 34(3): 272, pl. 19. 1903.-"[MEXICO. Michoacan:] . . . Los Frenos [properly Los Fresnos], 1850 m, mars 1898, [Langlasse] no. 52."-Holotypus, G! isotypi, G, GH, MEXU, NY (fragm), US (=NY Neg. 9088)!-Peiranisia quiedondilla (Micheli) Britton & Rose, N. Amer. Fl. 23(4): 262. 1930.

Cassia tapahuascana A. Molina, Ceiba 18(1-2): 98. 1874.-"Honduras: Dept. El Paraiso: . . . Quebrada Honda, Montana Tapahuasca, entre San Lucas y Morolica . . . Molina 14234;. . . pine forest of Tapahuasca, between Manzaragua and San Lucas, alt. 1400 m., Nov. 24, 1966, Molina 18734 . . -Holotypus, designated by Molina, l.c., Molina 18734, F! = NY Neg. 9684; isotypus (not seen), EAP; paratypus, Molina 14234, F (2 sheets)!

Weakly arborescent shrubs at anthesis commonly 1-4.5 m, in undisturbed forest sometimes becoming slender trees up to 7(-10) m, with terete annotinous and older branches and usually deeply sulcate hornotinous branchlets, varying from quite glabrous below the ovary to thinly pilosulous except for always glabrous sepals, the lfts commonly quite glabrous on both faces or glabrous except for a tuft of hairs dorsally in the anterior basal angle of midrib, sometimes pilosulous over whole lower (and exceptionally also upper) face, the inflorescence of 2(-4)- fld racemes either leafy-bracteate and formed of either single racemes or of 2 (several) together on condensed brachyblasts axillary to coeval lvs, or more commonly, at least at maturity, corymbose- or thyrsoid-paniculate and ± exserted.

Stipules linear-attenuate (2.5-)4-7.5(-10) x 0.2-0.5(-0.7) mm, rarely expanded and up to 1 mm wide.

Major lvs 5.5-11(-12) cm, those of branchlets (especially late in season, not further described) shorter and simpler; petioles (12-)15-30 mm, 3-5 times as long as first segment of rachis; rachis 4-8(-9.5) cm; gland between proximal pair 1.5-3(-4.2) x 0.4-1 mm; petiolules 0.6-1.8 mm; lfts (8-)9-15(-17) pairs [caveat: of summer-flowering branchlets often fewer!], the distal pair no longer or a trifle shorter than their neighbors, in outline oblong, oblong- or obovate-oblanceolate obtuse or deltately subacute, 11-26(-36) x 3-10(- 11) mm, (1.8-)2-4 times as long as wide, the simply pinnate venation of midrib and 5-9(-11) pairs of major camptodrome secondary veins immersed and usually imperceptible above, visible but scarcely or not prominulous beneath.

Peduncles (8-)10-26(-35) mm; racemes 2-4-fld; pedicels 10-16(-20) mm; long sepals (6-)7- 11 (- 12) mm; long petals (16-) 18-29(-32) mm; androecium usually glabrous, the filaments of 4 median stamens either free or partly united 1-2.2 mm, those of 3 abaxial ones free 2-3.8 mm, the anthers of 4 median stamens 3.8-5.5 mm, conic-pointed distally, the body of 3 abaxial ones (3-)3.6-7(-8) mm, the beak (1.2-) 1.8-3.6 mm; style 1.2-2 mm.

Stipe of pod 4-7 mm, the body 5-10 x (0.5-)0.6-0.75(-l) cm, the valves simply mounded over the seeds; seeds either ovate or oblong in outline, 3-4.5(-6) x 2-2.5 mm, the testa brown-olivaceous, the ovate-elliptic or (in longer seeds) linear- oblong-elliptic areole (0.9-) 1.2-2.4(-3.5) x 0.4-0.7 mm.-Collections: 63.

Glades, clearings and margins of oak-, pine- and mixed deciduous upland forest, persisting and sometimes locally abundant in regenerating brush, 900-2100(-2300) m and occasionally lower (in Honduras down to 600, in Chiapas to 700 m), common along and near the Continental Divide from s. Mexico (highlands of Chiapas) through Guatemala into w. El Salvador (Ahuachapan, Sta. Ana, Sonsonate), thence e., becoming rarer and scattered, through w.-centr. Honduras (Cortes, Distrito Central, El Paraiso) into Nicaragua (Jinotega); unknown from Oaxaca, but reappearing in scattered stations around the periphery of the Balsas Depression in s. Mexico, on and near the summit of Sa. Madre del Sur in Guerrero and the s. slope of Cordillera Neovolcanica in Michoacan.-Fl. X-III, occasionally in summer.

As defined by the foregoing description, var. quiedondilla is the commonest and most widely dispersed representative of the S. pallida complex in the relatively moist and cool, primitively wooded uplands of southern Pacific Mexico and northwestern Central America, a zone occupied in Costa Rica by the closely related var. cordillerae, different in the glandiform seta terminating the leafstalk, and shared locally, in Guatemala only, with var. longirostrata and var.foliolosa. The two last-named resemble var. quiedondilla in their penniveined, not reticulate leaflets and are collectively distinguished thereby from var. pallida which, largely vicariant in the tierra caliente at the same latitudes but ascending occasionally, perhaps only as a weed, into the uplands, differs further in its short petiole and from all but var. longirostrata in the strongly accrescent distal leaflets. Common characters of the highland varieties are a broad pod and a relatively large seed, large areole, or both. The var. quiedondilla differs from var. longirostrata in the more numerous, less strongly graduated leaflets and from var .foliolosa in its less numerous (9-17, not 17-31 pairs) of larger ones.

The differences readily apparent between specimens of var. quiedondilla, though very likely in part genetic, are certainly often merely edaphic or seasonal. Long primary cauline leaves that at early anthesis may subtend single 2-flowered racemes, or leafless branchlets sometimes contracted into a brachyblast bearing a fascicle of 2-3 racemes, give way distally, early or late in the season, to much shorter and simpler ones, these finally reduced to bracts of an exserted, loosely or compactly corymbose or thyrsoid panicle. Much fruiting material, indeed, lacks the long leaves entirely, as do leafy branchlets of the second order of ramification leading to the panicle; such specimens in fruit may be recognized by their relatively broad flat pod and by the individual seed. Transition between a leafy thyrse and a naked panicle of racemes is very gradual; both types occur in the same intermediate area but are seldom seen in any one collection from a given place. The typus of Cassia quiedondilla does, however, well illustrate the coincidence of two inflorescence types, the terminal panicle as illustrated in the pro- tologue and the series of brachyblasts subtended by long leaves of mature branchlets illustrated by the isotypus at US. Phenetically identical branches have been collected in Chiapas and Huehuetenango; of the virgate leafy type cf. Ton 1865 (NY) and Holdridge 2284 (US), of the exserted paniculate one numerous examples at NY, F, and US.

In Sierra de Cuchumatanes in Quiche and Huehuetenango, Guatemala and in highland central Chiapas the beak of one, two, three or exceptionally of all four median anthers of var. quiedondilla dehisce by a U-shaped slit, exactly in the style of S. angustisiliqua. The plants so characterized are otherwise identical with sympatric ones with biporose median anthers and we regard this anomalous dehiscence as taxonomically vexatious, because it destroys the technical distinction we have drawn between S. pallida and S. angustisiliqua, but not taxonomically significant. A notable plant, ostensibly from Veracruz (Zacuapan, Purpus 2342, F, NY, but not the sheet so numbered at US) appears to represent a densely pubescent state of var. quiedondilla not otherwise exactly matched; but there being some question of its provenance and the correctness of the label we have omitted Veracruz from our statment of dispersal pending modern verification of var. quiedondilla on the Gulf slope in Mexico.

The pollination of var. quiedondilla by bees, as seen in the mountains of Guerrero between Tixtla and Chilapa, is described in detail by Buchmann (Bull. S. Calif. Acad. Sci. 73(3): 171, fig. 1. 1974).