Dichrostachys Wight & Arn., Prod. Fl. Ind. Orient.: 271. 1834.
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https://dx.doi.org/10.3897/phytokeys.240.101716 |
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persistent identifier |
https://treatment.plazi.org/id/06D15CE4-53E1-5947-C9A8-92B0FEA9AD7C |
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scientific name |
Dichrostachys Wight & Arn., Prod. Fl. Ind. Orient.: 271. 1834. |
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Dichrostachys Wight & Arn., Prod. Fl. Ind. Orient.: 271. 1834. View in CoL
Figs 144 View Figure 144 , 145 View Figure 145 , 146 View Figure 146 , 158 View Figure 158
Cailliea Guill. & Perr., Fl. Seneg. Tent.: 239. 1832, nom. rej. vs. Dichrostachys Wight & Arn. Type: Cailliea dichrostachys Guill. & Perr., nom. illeg. [≡ Mimosa nutans Pers. (= Dichrostachys cinerea subsp. africana Brenan & Brummitt)]
Type.
Dichrostachys cinerea (L.) Wight & Arnott [≡ Mimosa cinerea L.]
Description.
Shrubs or small trees to 7 m (Fig. 144K View Figure 144 ), branching from base, unarmed or the branches modified into thorns, branches plagiotropic, young stems terete, rarely angled with corky ridges; older stems terete, brachyblasts present, clothed in distichous fused stipule bases. Stipules monomorphic, ovate-triangular, striate, stramineous, persistent. Leaves bipinnate; extrafloral nectaries usually between the proximal pair of pinnae but sometimes at mid-petiole and sometimes additional glands between more distal pinnae, usually cylindrical, raised; pinnae 1-15 (20) pairs; leaflets 1-40 pairs per pinna, linear to ovate, venation brochidodromous to fused eucamptodromous, obscure to abaxially raised, pubescent to glabrous. Inflorescences pedunculate condensed spikes (Fig. 145K, L View Figure 145 ), the peduncle often bearing a few lanceolate bracts, 1-3 in leaf axils of new growth or more frequently on the brachyblasts, not forming paniculiform secondary inflorescences; bracteoles subtending each flower carinate, 1-nerved; spikes composed of sterile flowers proximally, rarely sterile flowers absent ( D. kirkii f. puccioniana ), fertile flowers distally, and often a few functionally staminate flowers in between. Flowers sessile, pseudopedicels absent; sepals and petals valvate in bud; sterile flowers smaller than the hermaphrodite ones with 10, showy, filamentous or flattened and ribbon-like staminodia, bright rose-pink fading white; functionally staminate flowers similar to bisexual ones but either lacking or having only a rudimentary ovary; hermaphroditic flowers with a 5-lobed calyx, petals 5, free or sometimes centrally or basally connate, usually linear or lanceolate, 1-nerved; stamens 10, the filaments either exserted or included at anthesis, anthers with a spherical, long-stipitate, apical gland or gland absent (Madagascar); pollen in 16-grained, acalymmate polyads shed as single grains or calymmate polyads of 8-16 grains, exine verrucate to reticulate; ovary oblong to ovate, sessile, densely strigose with silky white hairs, style exserted at anthesis, white, stigma punctate. Fruits sessile, dorsiventrally compressed, elastically dehiscent from the apex (Fig. 146P View Figure 146 ) and coiling after dehiscence, or indehiscent (Fig. 146O View Figure 146 ); pericarp coriaceous in elastically dehiscent species, woody in the indehiscent ones, the sutural ribs well defined but not greatly enlarged and overtopping the valves, the interior of the fruit usually invaginated between the seeds. Seeds obliquely oriented, ovate to rhomboidal, pleurogram either U-shaped or forming nearly a complete oval on the face of the seed.
Chromosome number.
2 n = 28 (36, 54, 56, 78) in D. cinerea ( Atchison 1951) which forms a poorly understood polyploid series ( Brenan and Brummitt 1965).
Included species and geographic distribution.
ca. 13-14 species, D. cinerea with many varieties. One species native and widespread in Africa, India, and Australia, and widely introduced and weedy elsewhere; one species restricted to the Horn of Africa; one endemic to Socotra; one endemic to Australia; 10 species in Madagascar (Fig. 158 View Figure 158 ).
Ecology.
Many diverse habitats, from open savannas and seasonally dry forests to arid tropical scrub. Mostly deciduous. Dichrostachys cinerea is a problematic weed in many parts of the tropics, where it can form pure stands and outcompete native vegetation.
Etymology.
From Greek, di - (= two), chroma (= colour) and - stachys (= spike), in reference to the bi-coloured spicate inflorescence found in the genus (Fig. 145K, L View Figure 145 ).
Human uses.
Wood used for fuel and for small tools, leaves and fruits are important sources of livestock forage. Dichrostachys cinerea has been used in soil reclamation projects and as an ornamental ( Pedroso and Kaltschmitt 2012).
Notes.
As currently circumscribed, Dichrostachys is non-monophyletic (Fig. 143 View Figure 143 ; Hughes et al. 2003; Luckow et al. 2005; Ringelberg et al. 2022). This non-monophyly will be dealt with via erection of a new genus, Famoha ined. (Luckow in prep.) in a forthcoming monograph that includes a species-level taxonomic account of the four closely related genera: Dichrostachys , Gagnebina , Alantislodendron , and the upcoming new genus.
Taxonomic references.
Brenan and Brummitt (1965); Thulin (1989).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.