Hypolytrum Pers. (Persoon 1805: 70)

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

Hypolytrum Pers. (Persoon 1805: 70)

Type species.

Hypolytrum latifolium Rich. ex Pers. [= Hypolytrum nemorum (Vahl) Spreng.]

Description of the genus.

Perennials, moderately robust to robust; rhizomatous or stoloniferous; rhizomes often woody, roots coarse. Culms trigonous or cylindrical, either laterally scapose and bearing reduced leaves at the base (cataphylls), or central with 1-several nodes and bearing well-developed leaves. Leaves eligulate, 3-ranked, sometimes pseudopetiolate; leaf sheath of basal leaves open adaxially; leaf sheath of cauline leaves tubular; blade linear to oblong-lanceolate or reduced (often in basal leaves), with 3, well developed principal veins, margin entire or many small teeth, gradually or abruptly narrowed at apex. Involucral bracts small, scale-like, or large and leaf-like, not sheathing, patent to reflexed. Inflorescence terminal, paniculate, corymbose or capitate, the ultimate branches subtending small clusters of spikes. Spicoids composed of 2(-3) floral bracts, each subtending 1 stamen (male flowers), often connate to varying degrees, the lower two followed by a bare pistil (female flower). Florets unisexual; perianth absent. Stamens 1; anthers oblong to linear, latrorsely dehiscent, without extended connective tip; filaments filiform, exceeding spicoid bract. Style 2-fid, exserted; base distinct or not, thickened or not, more or less persistent. Nutlets obovoid to ellipsoid, dorsiventrally biconvex, smooth, costate, wrinkled, tuberculate or spongious.

Distribution and ecology.

Hypolytrum is widely distributed in the tropics ( POWO 2022). It grows in humid forests, on the edges of wetlands including mangroves, and in rocky areas near sea level. A single species of the genus, i.e. Hypolytrum nudicaule Juss. ex Cherm. (Fig. 2 ), occurs in eastern and northern Madagascar.

Figures

Figure 2. Hypolytrum nudicaule. A. Habit. B. Inflorescence. C. Plant base. All photos taken on Nosy Boraha Island by Justine Faure (https: // www. inaturalist. org / observations / 132556611), reproduced with permission from the photographer.