Flora of North America species comparison

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Desmanthus virgatus

wild tantan
Habit Herbs, prostrate to decumbent, much-branched from base, to 1.5 dm, not woody at base; taproot cylindric, bark brown.
Stems

glabrous or sparsely pubescent with short white hairs along ribs, glabrescent.
Leaves

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.
Peduncles

0.6–4 cm, 1–5.2 cm in fruit.
Flowers

stamens 10;

staminodia 1.5–7.5 mm;

style not exserted beyond stamens.
Legumes

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.
Heads

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.
2n

= 28.

Desmanthus virgatus
Phenology Flowering and fruiting Apr–Nov.
Habitat Railroad tracks, pastures, roadsides, along city streets, coastal thickets, beaches.
Elevation 0–1000 m. [0–3300 ft.]
Distribution
from FNA
FL; LA; TX; Mexico; Central America; South America; West Indies
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)
Source FNA vol. 11.
Parent taxa Fabaceae > subfam. Caesalpinioideae (Mimosoid clade) > Desmanthus
Sibling taxa
D. acuminatus, D. bicornutus, D. brevipes, D. cooleyi, D. covillei, D. glandulosus, D. illinoensis, D. leptolobus, D. leptophyllus, D. obtusus, D. reticulatus, D. velutinus
Synonyms Mimosa virgata, D. depressus, D. virgatus var. depressus
Name authority (Linnaeus) Willdenow: Sp. Pl. 4: 1047. (1806)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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