Monographs Details: Senna pallida var. macdougalliana 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
Description:Variety Description - Treelets to 3.5 m with flexuous subterete hornotinous branchlets, glabrous or almost so up to the ovary, the ample blue-green lfts completely so, the 2-fld racemes borne solitary or commonly 2-3 together on leafless nodiform brachy- blasts axillary to coeval lvs, the large fls immersed in foliage. Stipules (little known), lance-subulate 2-2.5 x 0.5 mm. Major lvs 12-17 cm; petiole (15-)17-32 mm, at middle 0.7-1.2 mm diam, rounded dorsally, 1.8-2.3 times as long as first interfoliolar segment of rachis; rachis 7-11.5 cm, petiolar gland between proximal pair subsessile, broadly oblanceolate in profile, 2-2.8 x 0.8-1.5 mm; lfts up to 7-10 pairs, accrescent upward along rachis, in outline elliptic obtuse to deltately subacute, the distal pair 32-60 x 12-21 mm, 2.3-3 times as long as wide, the venation of 7-10 very slender pairs of camptodrome secondary veins immersed above, faintly raised beneath, a weak irregular tertiary venulation discolored but immersed. Peduncles 10-29 mm, pedicels 18-32 mm; sepals apparently early reflexed, the long inner ones 8.5-10 mm; long petals 26-31 mm; androecium glabrous, the filaments of 4 median stamens either free or confluent at base 1.4-1.8 mm, those of 3 abaxial ones 4-5.5 mm, the anthers of 4 median stamens 4.5-5.5 mm,’ those of 3 abaxial ones 6-9 mm, the beak 2-2.5 mm; style 1-1.5 mm. Stipe of pod (poorly known) 7-9 mm, the body ±11-12 x 0.7 cm; seeds unknown except as withered ovules but the areole early becoming ±2 mm long - Collections: 5. [Key: "Appendage terminal of lf-stalk modified into a gland resembling that between proximal pair of lfts; local either in highland centr. Costa Rica or in s. Mexico (Mexico, Oaxaca, Veracruz). Lfts of larger lvs 9-12 pairs; ovules 26-52; either the larger lfts over 2 cm long or the pod over 12 cm long. Plants of s. Mexico. Larger lfts 25-60 cm long; ovules ±25-32; pod 7-13 X 0.6-0.85 cm; either Pacific lowland Oaxaca or s. Mexico. Margin of lfts plane; venation of lfts immersed on upper face; Sa. Madre del Sur in s. Oaxaca."]

Distribution and Ecology - Habitat not recorded, but to be expected in the oak belt, 300-1200 m, apparently very local, known only from the Pacific slope of Sa. Madre del Sur in s. Oaxaca (Juquila; n. of Pochutla; Candelaria Loxicha).- FL II-III.

Discussion:In the diagnosis we have compared this handsome floriferous variety with var. trichocraspedon, similar in the glandiform seta of the leafstalk and in the relatively ample, prevailing elliptic leaflets; but these are plane, not conspicuously revolute, and smooth on the upper face, the secondary pinnate venation and midrib being fully immersed into the epidermis. The general aspect of var. macdougalliana instantly and compellingly suggests var. geminiflora, which has been collected both at Juquila and in the neighborhood of Pochutla, and must be actually or very nearly sympatric; but this differs in its normal setiform appendage to the leaf-stalk, in the sharply reticulate upper face of the leaflets, and in the small areole of the seed-faces, ±0.5 not 1-2 mm diameter. The also very closely related but distantly allopatric Costa Rican var. cordillerae, which has the same glandiform seta and the same large areole, differs precariously in its strongly bicolored leaflets, dull dark green above and pallid beneath, not pallidly glaucescent on both faces, and perhaps in the (still too little known) narrower pod. The variety was collected first in March, 1849, somewhere in Oaxaca, by Galeotti (no. 3469, NY), very likely in the Sierra Madre del Sur, but the station not recorded. We dedicate the variety to Thomas MacDougall, whose collections of this group of Interglandulosae from remote places in Oaxaca have been especially helpful and challenging.
Distribution:Oaxaca Mexico North America|

Common Names:Flor de Nixtamal