Senna argentea (Kunth) 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, collected by Humboldt & Bonpland IV. 1803 (fr), labelled ‘no. 3948, Mescala,’ P-HBK! isotypus, B-WILLD 7951!—Earleocassia argentea (H.B.K.) Britton ex Britton & Rose, N. Amer. Fl. 23(4): 250. 1930.
-
Synonyms
Cassia argentea Kunth, Earleocassia argentea (Kunth) Britton, Cassia longicoma Greenm.
-
Description
Species Description - Precociously flowering, weakly suffrutescent 1-few-stemmed (acc. Kunth fruticose many-branched) herbs from blackish roots at anthesis 1-5 (acc. Kunth-12) dm, softly gray-pilosulous with accumbent shorter hairs and the stems, lf-stalks and peduncles in addition pilose with fine lustrous horizontal setae up to 2.5-3 mm, the short vesture of stems retrorsely, of lfts antrorsely accumbent, the foliage subbicolored, yellowish-tinged above and silvery-gray beneath, the few-fld racemes axillary to and ± as long as almost all primary lvs, produced over a long season, the ripe pods and expanded fls often contemporary. Stipules erect or in age spreading-declined, thinly herbaceous, narrowly lance- attenuate 4-9 x 0.5-1 mm, charged at base on one side with a stipitate gland like those between lfts, tardily dry deciduous. Lvs 5-8.5 cm; petioles including discolored but little swollen pulvinus 2-3.5 cm, at middle 0.5-0.8 mm diam, strongly 3-ribbed dorso-laterally, very narrowly sulcate ventrally ; rachis 1-2.7 cm; glands between proximal pair of lfts, slenderly stipitate, in profile 1.5-2.5 mm, the stipe pilosulous, the narrowly lance-fusiform acute reddish head 0.2-0.3 mm diam; pulvinules 1-2 mm; lfts 2 or 3 pairs, accrescent distally, the distal pair broadly obliquely obovate or elliptic-obovate obtuse mucronulate or apiculate 2.2-4 x 1-1.8 cm, 1.4-2.2 times as long as wide, at oblique base cordate on proximal and cuneate on distal side, the margin plane, the midrib and 4-5 pairs of weak secondary veins immersed or almost so above, prominulous beneath, tertiary venulation invisible. Peduncles stiffly ascending 3-6 cm; racemes loosely (l-)2-5-fld, the axis becoming (0-)3-20 mm; bracts 3-5 mm resembling stipules and like them sometimes subtended by a subulate gland, deciduous; mature pedicels 11-15 mm; fl-buds oblong-obovoid obtuse, finely setose; sepals thinly herbaceous, the inner glabrous and hyaline where covered in bud, all oblong-oblanceolate or -elliptic obtuse scarcely graduated 6.5-9 mm, deciduous with the petals; petals yellow glabrous, obovate-cuneate subequal 10.5-12.5 mm; androecium glabrous, functionally 7-merous, the stamens nearly isomorphic, the filaments 2.2-2.5 mm, the anthers slenderly lance-oblong almost straight 3-3.7 x 0.6 mm, brown with yellow stripe in the lateral grooves, at apex obtusely conic and dehiscent by an oblique pore; ovary densely white-pilosulous; style 0.6-1 mm, stout and a trifle dilated upward, at truncate apex 0.3 mm diam; ovules 28-36. Pod widely ascending, sessile or almost so, linear-oblanceolate attenuate at both ends, straight or slightly incurved 5.5-8 x 0.55-0.65 cm, moderately compressed but turgid, the green valves becoming papery brown with broad paler sutural margins, shallowly corrugated over the seeds, both minutely puberulent and strigose with coarser appressed setules up to 0.8-1 mm, dehiscent downward through both sutures but scarcely gaping; seeds 1-seriate, each turned with broad face appressed to its neighbors and oriented obliquely basipetal to the pod’s long axis, compressed-pyriform (2.3-)2.5-3.2 x 2.2-2.8 mm, the testa khaki-brown sublustrous, incipiently colliculate but not boldly wrinkled, the round or broadly elliptic areole 0.4-0.5 mm diam.—Collections: 13.
Distribution and Ecology - Habitat not recorded, but to be looked for in matorral on limestone, 450-1450 m, local in the e. arm of Balsas Depression in extreme e. Michoacan, Morelos, and adjoining Guerrero and Puebla, thence s.-e. into centr. Oaxaca.—Fl. and fruiting continuously IV-II(-IV), perhaps often monocarpic.
-
Discussion
Senna argentea and the two species next in order, S. arida and S. apiculata, are closely related and could perhaps be considered as no more than varieties of one. They differ collectively from S. crotalarioides in the retrorsely oriented short pubescence of the stems, in the presence of a stipitate gland at base of the stipules as well as between the leaflets, and in the more or less colliculate (not smooth) testa of the seeds, a seldom observed character that will, however, need confirmation in future collections. In the short thick style, only 2-3 times as long as its apical diameter, S. argentea resembles S. arida only, and differs from it in the elongate pod (4-8 not 3-4 cm) which, furnished with about the same number of ovules, accommodates the ripe seeds in a single vertical rank, not doubled up, as in all kindred species, into two interlocking rows. The long lustrous setae of the stems, so striking superficially, offer a practical diagnostic feature so far as known at present, but cannot be relied on in the context of the group. Our description of S. argentea records the fruticose stature assigned to it in the protologue, but we suspect that an error of memory or of interpretation is involved. The type-collection could well have come from a softly woody herb like all examples of S. argentea since encountered.
-
Distribution
Michoacán Mexico North America| Morelos Mexico North America| Guerrero Mexico North America| Puebla Mexico North America| Oaxaca Mexico North America|