Cassiinae pt 1 NY-Botanical_gardens_Vol. 35_1 - Copy.pdf - Antbase

1982] CASSIINAE—SENNA 271
cordate proximally and cuneate distaUy, the margin plane, the slender midrib
always and sometimes 2-5 pairs of weak secondary veins finely prominulous
beneath, the blades otherwise veinless.
Peduncles 1.3-4 cm; racemes shortly or subumbellately 2-5-fld, the axis 1^
mm; bracts narrowly lanceolate 3-5 mm, often persistent into anthesis, then de­
ciduous; pedicels (4-)5-l2 mm; young fl-buds obovoid, pUosulous or strigulose;
sepals subequal, oblong- or ovate-elliptic obtuse (4.5-)5-6.5(-7) mm; corolla and
androecium of S. crotalarioides except a trifle smaUer, the petals (7.5-)8-13 mm,
the filaments of 5 abaxial stamens 1.9-2.7 mm, their anthers (2-)2.5-3.7 x 0.5-0.7
mm; ovary densely white-pUose; style filiform glabrous 2.5-3.7 x 0.1-0.2 mm;
ovules 14-21.
Pod essentially that of S. crotalarioides in posture, structure and texture of
valves but averaging smaUer, in outUne oblong-elliptic (8-)10-13(-14) x (4.5-)5-6
mm, the valves pilosulous with stiff, narrowly or widely ascending setules up to
0.5-1.1 mm interspersed with minute thickened trichomes; seeds (httle known)
apparently like those of S. crotalarioides, the testa smooth.
Senna demissa, endemic to dry hmestone mountains ofthe central Chihuahuan
Desert and adjoining west slope of Sierra Madre Oriental, is closely related to
the vicariant S. crotalarioides, with which it shares antrorse or spreading (but
not retrorse) vesture of the stems, conspicuously elongate and long-persistent
glandless stipules, a filiform style, a short plump pod and smooth seeds. It differs
from S. crotalarioides in the smaller size of most parts, in the almost complete
stabihzation of leaflet number at two pairs, and reduction of ovules to 14-21 (not
22-32). Two weakly differentiated varieties are recognized:
Key to the Varieties of 5. demissa
1. Stems decumbent from a loosely branched, often adventitiously rooting caudex, at anthesis
1-3.5 dm, pilose-pilosulous with spreading-ascending or horizontal hairs up to 0.8-2 mm;
relatively widespread in centr. and s.-e. Coahuila, disjunct in s.-w. Tamaulipas.
76a. var. radicans (p. 272).
1. Stems compactly tufted 4-10 cm, strigulose with subappressed hairs 0.6-1 mm; local in
extreme s. Coahuila, adjacent Zacatecas and centr. Nuevo Leon. 76b. var. demissa (p. 271).
76a. Senna demissa (Rose) var. radicans (Irwin & Barneby) Irwin & Barneby,
Phytologia 44(7): 499. 1979. Cassia demissa var. radicans Irwin &
Barneby, Sida 6(1): 9. 1975.—"MEXICO. Coahuila: s.-w. end of Sa.
de la Fragua, 1-2 km n. of Puerto Colorado, 2.IX.1941 (fl, fr), /. M.
Johnston 577^."—Holotypus, TEX! isotypus, GH!
As described in key.—Collections: 11.
HiUsides and canyons, in izotal and chaparral and ascending into pinyon wood­
land, 1400-2100 m, scattered through the mountains of centr. and s. CoahuUa
from Sa. de la Madera s. through Sas. de Fragua and de Organos to Sa. de Parras
and the Sa. Madre immediately s.-e. of Saltillo; collected once in s.-w. Tamau­
lipas, close to a population of 5. crotalarioides, and perhaps there intergradient.—
Fl. VI-IX.
The eariiest coUection of var. radicans, Gregg 244, was misidentified by Ben­
tham (1871, p. 530) as Cassia vogeliana, i.e. the setose aspect of 5. crotalarioides.
The second. Palmer 281, contributed to Rose's original concept of C. demissa.
We here give var. radicans precedence over the rarer and, we suspect, more
derived var. demissa, which represents the pygmy extreme of its group.