Desmanthus covillei
Desmanthus virgatus
Coville's bundleflower
wild tantan
glabrous.
glabrous or sparsely pubescent with short white hairs along ribs, glabrescent.
2–5 cm;
stipules persistent, 1.5–2.5 mm, with flared, membranous bases, glabrous;
petiole 5–15 mm;
pinnae 1–3(or 4) pairs;
nectary sessile or stipitate, crateriform, interpinnal between proximal pair of pinnae;
leaflets 16–34, blades 4–8 mm, venation obscure except for eccentric midvein, sometimes also 1 short, arcuate vein from base, surfaces glabrous.
1–3[–6.5] cm;
stipules persistent, 2.1–9 mm, with membranous, prominently veined auricle opposite petiole, glabrous or pubescent;
petiole 1–5 mm;
pinnae 2–5 pairs;
nectary present, sessile, crateriform, interpinnal between proximal pair of pinnae;
leaflets 22–46, blades 2.7–7 mm, venation obscure except for eccentric midvein, surfaces glabrous.
1–2.3 cm, 1–3.5 cm in fruit.
0.6–4 cm, 1–5.2 cm in fruit.
stamens 10;
staminodia 7.5–17 mm, showy;
style exserted 3–5 mm beyond stamens.
stamens 10;
staminodia 1.5–7.5 mm;
style not exserted beyond stamens.
brown, straight to slightly arcuate, linear, constricted between seeds, dehiscent along both sutures, 5.5–13 cm × 2.7–4 mm, apex acute, rarely with short beak to 3 mm.
reddish brown to nearly black, straight or weakly falcate, linear, not constricted between seeds, dehiscent along both sutures, 2.2–6[–8.8] cm × 2.5–4 mm, apex acute to attenuate.
1 or 2 per axil, 23–43-flowered;
sterile flowers 5–16 per head; staminate and bisexual flowers 8–30 per head.
1 per axil, 3–22-flowered, sometimes only bisexual flowers present;
sterile flowers 0–8 per head; staminate and bisexual flowers 3–14 per head.
= 28.
Desmanthus covillei
Desmanthus virgatus
Desmanthus covillei is the only shrubby member of the genus in the flora area. It is widespread in western Mexico but known in the flora area only from the Tucson Mountains in Pima County. The relatively large, showy inflorescences and large fruits are diagnostic.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Desmanthus virgatus was the umbrella species in the genus for any taxon with inconspicuous flowers and unspecialized legumes; D. acuminatus, D. brevipes, and D. glandulosus have at times been considered varieties of this species, and D. leptophyllus and D. pernambucanus were synonymized with it in the tropics. The confusion is understandable because species differ in characteristics that may be difficult to see on a herbarium specimen, such as habit, degree of branching, taproot color and shape, and sleep movements of the leaves. Common garden studies (M. A. Luckow 1993) demonstrated that such characteristics are not phenotypic plasticity but have a genetic basis. In the flora area, D. virgatus is less variable than in Mexico, where one sees more erect forms with larger fruits and more flowers per inflorescence.
Desmanthus virgatus, as here circumscribed, is found throughout warmer areas in the New World; Old World species that have previously been considered D. virgatus are best referred to D. pernambucanus. Desmanthus virgatus has been intensively studied as a potential source of livestock feed for tropical areas.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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