Costularia C.B.Clarke (Clarke 1898: 274)

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

Costularia C.B.Clarke (Clarke 1898: 274)

Type species.

Costularia natalensis C.B.Clarke

Description of the genus.

Perennials, small to tall, tufted or more rarely shortly rhizomatous, caudex sometimes present. Culms scapose or with few nodes. Leaves usually basal and cauline; basal leaves with poorly defined sheaths; cauline leaves enveloping up to 1/2 internode length; spirodistichous, eligulate; blade sometimes deciduous, margins scabrid. Involucral bracts more or less leaf-like, sheathing. Inflorescence terminal, contracted paniculate. Spikelets few to numerous. Glumes several, distichous, deciduous, of increasing length, the upper (1-)2 glumes each subtending a floret, enclosed by the wings of the next glume. Lower floret functionally male rarely bisexual or absent, upper floret bisexual or functionally female rarely functionally male. Bristles 6, fimbriate to ciliate, mostly longer than the nutlet and deciduous with it. Stamens 3; anthers long linear, briefly apiculate or not. Style 3-fid; base often distinct (at anthesis), thickened, persistent, often scabrid. Nutlets ovoid or oblong, rounded trigonous, often 3-ribbed, more or less stipitate, beaked, surface smooth or rugulose.

Distribution and ecology.

Costularia occurs in southeastern Africa, Madagascar, the Mascarenes, and Seychelles. It grows on rocky ground in forest, grassland, or ericoid vegetation, sometimes along streams or in swamps, usually at higher elevations. In Madagascar, Costularia is known from north to south along the mountain ridge and high elevation areas, including the Central Highlands. The genus was recently monographed ( Larridon et al. 2019), and 11 species are native to Madagascar, including e.g. Costularia itremoensis Larridon (Fig. 4B ) and Costularia pantopoda C.B.Clarke (Fig. 9 ).

Figures

Figure 4. A. Coleochloa setifera. B. Costularia itremoensis. C. Eleocharis acutangula. All photos taken in the Itremo Massif Protected Area by Fitiavana Rasaminirina.

Figure 9. Costularia pantopoda var. pantopoda. A. Habit. B. Inflorescence matching the habit. C. Spikelet. D. Lowest glumes of spikelets. E. Rest of glumes lower to upper, abaxial view. F. Bisexual flower. G. Male flower. H. Nutlet. Scale bars: A-B = 3 cm, C-H = 3 mm. All from Larridon et al. 2010 - 0144. Drawn by Juliet Beentje, reproduced with permission from the artist, originally published in Larridon et al. (2019).