Chamaecrista flexuosa var. texana (Buckley) 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

Chamaecrista flexuosa var. texana (Buckley) H.S.Irwin & Barneby

Type

Holotypus, PH! isotypus (fragm ex. hb. Durand.), GH!—Chamaecrista texana (Buckley) Pennell, Bull. Torr. Club 44: 344. 1917.

Synonyms

Cassia texana Buckley, Chamaecrista texana (Buckley) Pennell, Cassia itzana Lundell

Description

Variety Description - Root (at least sometimes in Texas) tuberously fusiform, often deeply penetrating, its crown buried and giving rise to subterranean woody (rootlike) caudex- branches; stems humifuse, 1-5 dm; pubescence less variable than in var. flexuosa, mostly of incurved hairs <0.5 mm, occasionally on stipule-margins, upper stems and pedicels mixed with weak setae up to 0.6-1 mm, the lfts ciliolate, but either glabrous or pilosulous dorsally; lvs 1.5-4.5 cm, the expanded blade ovate or lance-ovate in outline; petiolar gland 1 (—2), 0.15-0.35 mm diam, often concealed in the petiolar sulcus but sometimes elevated on a thick stalk as long as its diam; lfts of adult lvs 9-21 (-25) pairs, 1-8.5 mm; pedicels 2-4.2 cm; sepals red-brown 5-7.5 mm, often proportionately wider than in var. flexuosa; petals bright yellow, up to 10.5-16 mm.—Collections: 35. [Key: "Major cauline lvs 1.5-4.5 cm, with 9-20(-25) pairs of lfts; pedicels either longer or only a trifle shorter than the lf-stalk; pod 2.5-4.7 cm, 8-12-seeded; s. Texas to s. Mexico, where confluent with the preceding."]

Distribution and Ecology - Sandy plains, sand flats behind barrier beaches, and dunes, sometimes weedy on roadsides and in old fields, 1-500 m, locally plentiful on the coastal plain of s. Texas (s.-ward from Maverick, Karnes and Bastrop cos) and Tamaulipas above Tropic of Cancer; disjunct on the n. coast of Yucatán (Progreso and vicinity); and along the Pacific coast of s. Mexico from Colima to Isthmus of Tehuantepec, occasionally inland to the floor of the Balsas Depression in Guerrero, here passing imperceptibly into var. flexuosa.—Fl. II-V n.-ward, VI-III s.-ward.

Discussion

The first collection of var. texana, the only one known to Bentham (Berlandier 2427), was provisionally referred by him (1871, p. 578) to Cassia procumbens, but noted as different in several features. In modem times it has been maintained as a distinct species, and no allusion has been made to the multiple similarities in habit, stipules, leaf and flower to the widespread tropical Ch. flexuosa. Britton & Rose (1930, p. 278, 284) placed Chamaecrista flexuosa and Ch. texana in separate series, the former in monotypic Flexuosae, the latter in Deeringianae, groups supposedly, but to us imperceptibly, different in texture of the leaflets. As known, and it is there best known, from the Gulf Coastal Plain of southern Texas and Tamaulipas, Cassia texana does at first sight appear quite distinct, compared with average Venezuelan or Brazilian Ch. flexuosa, in its humifuse stems, short leaves, relatively few leaflets, and long pedicels that raise the flowers beyond the subtending leaf. Furthermore the average calyx is shorter, the average pod shorter and fewer-ovulate. This idealized picture of abrupt contrasts fades into indistinctness when we consider those southern Mexican populations, traditionally referred to C. flexuosa, in which short leaves composed of 21 or fewer pairs of leaflets are combined with pedicels either longer or shorter than themselves and resemble in every single feature (even if not in all simultaneously) some individual Texan plants. The early leaves of tropical, long-leaved C. flexuosa are essentially identical in length and leaflet-number with the adult leaves of largely extratropical C. texana, in which it appears that a juvenile condition persists the length of the stem, or, if one prefers, the ontogenetic sequence of shorter to longer leaves upward along the stem fails to be carried out. Such an occasional failure would handily explain the random appearance in Paraguay of plants (Archer 4742, US) with no more than 16-19 pairs of leaflets. On the Brazilian Planalto the petals of typical var. flexuosa commonly open pale yellow and by mid-day fade pinkish-brown, as in the related and sympatric C. parvistipula; whereas in typical var. texana they open golden yellow and fade orange-brown. But golden yellow flowers have been seen on the restinga of the Guanabara coast, and noted by collectors in inland Bahia and elsewhere. In Texas the root-crown is sometimes (Irwin 1209) rigid and deeply buried, fusiformly dilated, and gives rise to subterranean caudex-branches, each of which appears from superficial viewpoint to give rise to an independent plant. In tropical C. flexuosa the root-crown is superficial, and the root itself, varying from subfiliform (and short-lived) to a centimeter or more in diameter, sometimes dilated upward into a knotty platform or xylopodium, is apparently never tuberously enlarged. Too few collections show enough of the root-system to provide systematic information on this point, but the collected root of at least some Texan populations (e.g. Cory 55285, US; M. C. Johnston 5353, NY) show lateral rootlets arising from what appears to be an ordinary taproot without any indication of superimposed caudical structure. The population on the coast of Yucatan, described as C. itzana, was compared by Lundell with the "clearly allied" C. jalapensis, a species in our opinion entirely different in venation of the leaflets and supra-axillary pedicels. These plants do differ somewhat from Texan var. texana in slightly broader leaflets, looser pubescence, and shorter pedicels; but in no such fundamental feature as would lead us to believe in the existence of a specifically distinct type. Some dwarfed Ch. flexuosa from very dry sites in the Balsas Depression in Guerrero are intermediate in every sense between ideal vars. flexuosa and texana and are here arbitrarily disposed of according to the highest number of leaflets on the longest leaf.

Distribution

Texas United States of America North America| Tamaulipas Mexico North America| Yucatán Mexico North America| Colima Mexico North America| Guerrero Mexico North America|