Rhynchospora Vahl (Vahl 1805: 229)

Rasaminirina, Fitiavana & Larridon, Isabel, 2023, The genera of Cyperaceae of Madagascar, Plant Ecology and Evolution 156 (3), pp. 276-310 : 276

Rhynchospora Vahl (Vahl 1805: 229) nom. cons.

Type species.

Rhynchospora alba (L.) Vahl

Description of the genus.

Usually small to medium-sized perennials, rarely annuals; rhizomatous or with a poorly developed root system. Culms scapose or with 1-many nodes, rounded to trigonous. Leaves radical or radical and cauline; sheaths closed, ligule minute or absent. Involucral bracts leaf-like or reduced. Inflorescence very variable, paniculate, corymbose, anthelate or capitate, rarely pseudolateral. Glumes spirally arranged (rarely distichous), of increasing length to subequal, larger (1-)2-few glume(s) subtending a floret, enclosed by the wings of the next glume. Florets bisexual, the lowest few sterile and/or upper staminate (variable with species). Perianth bristles usually 3-6, or absent. Stamens (1-2-)3, inconspicuous. Style 2-fid, with base persistent (tubercle). Nutlets usually lenticular to globose. Embryo top-shaped in frontal view, root cap developed in a (sub)basal position, and first leaf primordium developed in a lateral position ( Carex -type embryo).

Distribution and ecology.

Rhynchospora is a cosmopolitan genus ( POWO 2022). It grows in seasonally wet to permanently flooded grassland, laterite outcrops, lake shores, stream sides, swamps, rice fields ( Browning and Goetghebeur 2017). Rhynchospora occurs throughout Madagascar; ten species are known including e.g. Rhynchospora holoschoenoides (Rich.) Herter (Fig. 11 ) and Rhynchospora angolensis Turrill (Fig. 12A ).

Figures

Figure 11. Rhynchospora holoschoenoides. A - B. Habit. C. Leaf sheath. D. Leaf apex. E. Inflorescence. F. Head of spikelets. G - H. Spikelet, complete and opened to show florets. I. Glume, lateral view. J. Nutlet. A-D from Robinson 6123; E, G, I from Robinson 1048; F from Robinson 1456; J from Renvoize 5598. Scale bars: A = 250 mm; B, E = 40 mm; C, F = 5 mm; G-I = 2 mm; D, J = 1 mm. Drawn by Jane Browning, reproduced with permission from the artist, originally published in Browning et al. (2020).

Figure 12. A. Rhynchospora angolensis; photo taken in the Itremo Massif Protected Area by Fitiavana. Rasaminirina. B. Carex sp.; photo taken in the Mantadia National Park by Vida. Svahnstrom.