Senna pendula
Senna armata
climbing cassia, valamuerto
desert senna, spiny senna
sclerophyllous, modified as phyllodes, 2–9 cm, thinly pubescent or glabrate;
stipules caducous;
extrafloral nectaries (0 or)1 or 2, highly reduced, on rachis, ± sessile;
leaflet pairs (0 or)2–8(–10), often irregularly inserted or absent, blades ovate, apex obtuse or subacute, 2–9 × 1–6 mm.
1 or 2-flowered;
bracts caducous.
8–21 mm.
monosymmetric;
calyx yellow;
corolla yellow, longest petal 7.5–13 mm;
androecium not heterantherous, stamens 7, staminodes 3;
anthers 3–4.3 mm, dehiscing by 1 apical pore, apical appendage 0;
gynoecium linear, ovules 6–12;
ovary hairy;
style incurved.
erect, flat or turgid, straight, linear, 20–45 × 5–6.5 mm, not or faintly corrugated over seeds, tardily dehiscent.
dark brown, ovoid.
pendula is often confused with close relative S. bicapsularis, which is absent from North America and has shorter pedicels, only to 5 mm (H.
. Irwin and R.
.
1982;
B.
et al.
).
Senna pendula
Senna armata
Varieties 18–20 (1 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Representative of the Mohave and Sonoran Deserts, Senna armata is the only North American senna displaying a highly xerophytic habit with green, nearly leafless stems (described as rushlike in the desert floras; R. M. Turner et al. 1995). Otherwise, this habit characterizes the unrelated group of a dozen species of Senna ser. Aphyllae (Bentham) H. S. Irwin & Barneby from aridlands in southern South America (H. S. Irwin and R. C. Barneby 1982). Owing to its highly xerophytic habit, S. armata was considered taxonomically isolated due to its xerophytic morphology (Irwin and Barneby), but, according to molecular phylogenetic analyses (B. Marazzi et al. 2006; Marazzi and M. J. Sanderson 2010), it is, in fact, included in the same clade as species of ser. Brachycarpae (Bentham) H. S. Irwin & Barneby (S. bauhinioides, S. covesii, S. lindheimeriana, and S. roemeriana, which also occur in North America).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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