Desmanthus covillei
Desmanthus
Coville's bundleflower
bundle flower
glabrous.
prostrate to decumbent or erect, young ones angled with corky ridges, glabrous or pubescent.
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.
alternate, even-bipinnate;
stipules present, setiform, base usually dilated, auriculate, striate-veined, membranous, 1 auricle sometimes developed into curled tooth under petiole; 1 extrafloral nectary usually present on rachis between proximal pair of pinnae, sometimes also between distal pinnae (in D. cooleyi, D. glandulosus, D. leptophyllus, and D. velutinus), rarely absent, sessile or stipitate; petiolate;
pinnae 1–18 pairs, opposite;
leaflets 10–90, opposite, short-petiolulate, blade margins entire, surfaces usually glabrous, sometimes pubescent or with few, scattered hairs, margins ciliate.
3–71-flowered, axillary, condensed spikes or heads, often with sterile flowers proximally, functionally staminate flowers in middle, bisexual flowers distally, sterile or staminate flowers sometimes absent;
bracts present, peltate, sometimes grouped into involucel at base of head.
1–2.3 cm, 1–3.5 cm in fruit.
stamens 10;
staminodia 7.5–17 mm, showy;
style exserted 3–5 mm beyond stamens.
mimosoid;
calyx cupulate, lobes 5, connate 1/3–1/2 length, dentate, acute;
corolla pale green or white, petals distinct, oblanceolate or linear, 1-veined;
stamens 5–10, distinct, filaments white or pale pink;
anthers dorsifixed to nearly basifixed;
ovary sessile, linear [ovate], glabrous [pubescent];
stigma funnelform; staminate flowers with rudimentary ovary;
sterile flowers with filamentous staminodia, white or pale pink.
legumes, sessile, straight or falcate, subterete to flattened, linear to oblong or falcate, leathery to papery [woody], dehiscent [indehiscent], glabrous.
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.
1 or 2 per axil, 23–43-flowered;
sterile flowers 5–16 per head; staminate and bisexual flowers 8–30 per head.
2–32, ovoid or rhomboid, obliquely, longitudinally, or laterally positioned in pod, testa hard, pleurogram present.
= 14.
Desmanthus covillei
Desmanthus
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.)
Species 25 (13 in the flora).
Species of Desmanthus have been studied over the past several decades as potential food and forage crops in both temperate and tropical areas because of the high protein content of the leaves and seeds, low levels of toxins, and a vigorous growth habit that allows them to persist in harsh environments. Attempts have been made to use D. illinoensis as a perennial seed crop, but it has been challenging to develop a reliable method to harvest the seeds from the dense infructescences (P. A. Kulakow 1999). Desmanthus illinoensis has been tested also as a temperate forage legume and can be used effectively in polyculture grasslands (V. D. Picasso et al. 2011). Extensive research on species from the D. virgatus complex (D. leptophyllus, D. pubescens B. L. Turner, D. virgatus) as a warm area/tropical forage crop has also been conducted, notably in Australia, where cultivars have been developed (W. R. Ocumpaugh et al. 2004).
The center of diversity for Desmanthus is in Mexico and the southern United States. Some species have disjunct distributions between the southern United States and southern South America (M. A. Luckow 1993).
Species delimitation in Desmanthus is challenging, and both flowering and fruiting material are often necessary for identification. Desmanthus is often confused with Neptunia. Stipules provide the best differentiating character; in Desmanthus they are setiform; in Neptunia they are triangular, membranous, and striate. One also often finds Acaciella angustissima among Desmanthus specimens. Flowering material is easily discerned using stamen number (10 per flower in Desmanthus, 15–many in Acacia, Acaciella, Mariosousa, Senegalia, and Vachellia); Acaciella angustissima also lacks a nectary on the petiole.
Desmanthus pernambucanus (Linnaeus) Thellung is planted in tropical climates as a forage crop and is a pantropical weed. It was reported as escaped in Florida by A. W. Chapman (1860; as D. diffusus Willdenow) and others, perhaps based on that report. No voucher specimens from Florida have been located so it is excluded here. It would key to D. leptophyllus, from which it differs in having 2–4 pinnae per leaf with 18–24 leaflets per pinna, pubescent stipules with curved auricles, and by being relatively few-branched from base, versus 4–8 pairs of pinnae with 32–72 leaflets per pinna, glabrous stipules with straight auricles, and relatively much-branched from base in D. leptophyllus. It has often been confused with D. virgatus; the latter has a shorter petiole and, usually, more pinnae than D. pernambucanus, as well as smaller stature.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Shrubs, 5–25 dm, annual growth terminal on existing branches; heads 23–43-flowered; staminodia showy, 7.5–17 mm. | D. covillei |
1. Herbs, subshrubs, or shrubs, 1.5–30 dm, new growth usually basal from woody taproot; heads 3–20(–71)-flowered; staminodia often inconspicuous, 0.5–11 mm. | → 2 |
2. Stamens 5; sterile flowers 0–2 per head; legumes oblong-falcate, and in tight, globose clusters, or straight, linear, and constricted between seeds. | → 3 |
3. Legumes incurved-falcate, not constricted between seeds, 4.5–7 mm wide, 3–4 times longer than wide, tardily dehiscent along abaxial suture; seeds inserted transversely; heads 20–71-flowered. | D. illinoensis |
3. Legumes linear, regularly constricted between seeds, 2.5–4 mm wide, 7+ times longer than wide, readily dehiscent along both sutures; seeds inserted longitudinally; heads 4–10-flowered. | D. leptolobus |
2. Stamens 10; sterile flowers 0–20 per head; legumes linear or oblong, not in tight, globose clusters, not or irregularly constricted between seeds. | → 4 |
4. Leaflet abaxial surface venation raised, reticulate; leaf nectaries usually absent. | → 5 |
5. Peduncles 2–6.2 cm in fruit; legumes dark brown with slightly raised venation on valves, apex obtuse; leaflet blades pubescent abaxially; sterile flowers 3–7 per head. | D. obtusus |
5. Peduncles 7–14 cm in fruit; legumes light brown with conspicuous raised, reticulate venation on valves, apex acute; leaflet blades glabrous abaxially; sterile flowers absent. | D. reticulatus |
4. Leaflet abaxial surface with eccentric midvein visible; leaf nectaries usually present. | → 6 |
6. Heads 21–60-flowered; styles exserted 3–5 mm beyond stamens; staminodia usually showy, 5–11 mm; legumes 4.6–10 cm. | → 7 |
7. Herbs erect, 1.5–3 m, unbranched or 2 or 3-branched from base; nectaries between proximal pair of pinnae or on petioles between stipels; stipules persistent; peduncles. | → 1 |
1. 5–3.7 cm. | D. bicornutus |
7. Herbs decumbent, to 0.5 m, much-branched from base; nectaries usually between proximal pairs of pinnae, rarely absent or also between more distal pairs of pinnae; stipules deciduous; peduncles 0.5–1.8 cm. | D. cooleyi |
6. Heads 5–22(–33)-flowered; styles slightly or not exserted beyond stamens; staminodia usually inconspicuous, 0.5–8(–10.5) mm; legumes 2.2–8.5(–10.6) cm. | → 8 |
8. Peduncles 0–0.5 cm. | D. brevipes |
8. Peduncles 0.6–4 cm. | → 9 |
9. Stems usually velutinous, rarely sparsely pubescent or glabrous; stipules densely villous. | D. velutinus |
9. Stems glabrous or densely to sparsely pubescent; stipules glabrous or pubescent but not villous. | → 10 |
10. Petioles 1–5(–6) mm; herbs prostrate to decumbent. | → 11 |
11. Legume apex apiculate; leaflets 14–24 per pinna; taproot napiform, bark red. | D. acuminatus |
11. Legume apex acute; leaflets 22–46 per pinna; taproot cylindric, bark brown. | D. virgatus |
10. Petioles (3–)5–16 mm; herbs or shrubs usually erect, sometimes decumbent. | → 12 |
12. Leaf nectaries between proximal and distal pairs of pinnae, sometimes between all pairs; Texas. | D. glandulosus |
12. Leaf nectaries usually between proximal pairs of pinnae, rarely also between distal pairs; Florida. | D. leptophyllus |
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