Ceropegia striata, a New Species of Asclepiadaceae in Central Madagascar

Abstract

A new species of Asclepiadaceae-Stapelieae from central Madagascar, Ceropegia striata Meve & Masinde, is described and illustrated. The delicate, tuberous twiner is characterized by linear corolla lobes and purplish, adaxially bulging vascular bundles resulting in the conspicuous striation of the completely whitish-greenish corolla. Due to similarities in vegetative growth and corona morphology, C. striata is probably nearest to C. madagascariensis Decaisne. In the conspectus of the Malagasy Ceropegia L., Meve and Liede (1994) listed 16 species in four sections, including section Dimorpha, which was formally established. Except for two varieties, all new Malagasy Ceropegia species described since Huber's (1957) revision belong to the section Dimorpha-a section consisting of several groups of highly variable and seemingly closely related species. Formally, C. striata would belong to the section Janthina of which C. madagascariensis is the type species. However, this section sensu Huber (1957) is an assemblage of not always closely related species and is therefore in urgent need of recircumscription. On Madagascar, C. striata is to be grouped with other twining species having a root tuber, thin and herbaceous stems, and membranous leaves, namely, C. humbertii H. Huber, C. madagascariensis Decaisne, C. saxatilis Jumelle & H. Perrier, and C. scabra Jumelle & H. Perrier. Ceropegia striata Meve & Masinde, sp. nov. TYPE: Madagascar. Central highlands, Vavavato Massif, ca. 22 km W Antsirabe, Betafo, 19045'S, 46?55'E, 1800 m a.s.l., 21 Dec. 1995, Grubenmann s.n. (holotype, ZSS; isotype, MSUN, in spirit). Figure 1. Affinis C. madagascariense Decaisne sed corolla albaviridi cum striis purpureis longistrorsis, lobis corollae angustis atropurpureis, ciliatis densis praeter margines, tubo corollae basaliter globuloso, corona glabra, lobis coronae staminalis spathiformibus planis, albis sed basaliter purpureis differt. Plant delicate, geophytic climber, herbaceous. Rootstock roundish, flattened tuber, ca. 20-28 mm diam., smooth, light brown. Stems herbaceous, deciduous, rarely branching, 1.0-2.5 mm diam., green with reddish tinge when exposed to direct sunlight, twining, glabrous. Leaves shortly petiolate, petiole 1-2 mm long, less than 1 mm wide, ?straight, canaliculate above, stipules minute, subulate, short-lived; leaf blades linear-elliptic to small lanceolate, acute, 10-30 x 5-8 mm, membranous, green, glabrous except for few recurved hairs along margins. Inflorescence extra-axillary, usually 1-flowered, subsessile with peduncle less than 1 mm long, 1 accompanying bract lanceolate-subulate, acute, ca. 1 mm long, pedicel + 5 mm long. Sepals lanceolate, flattened and appressed to corolla tube, ? 1 mm long. Corolla 25-35 mm long, abaxially glabrous; basal third of tube forming globoid inflation, ca. 7 x 6 mm, merging into narrow, cylindrical, ascending upper half of tube with conical mouth, ca. 12-15 mm long, basally 1-2 mm wide, apically 6-8 mm wide. Tube abaxially and adaxially whitish-greenish, with purplish adaxially bulging bundles, tube segments and each lobe contain 3 anthocyanin-pigmented bundles, each with central bundle strongest, pigmentation of each bundle restricted to outer phloem parenchyma plus an additional subcuticular stripe of parenchyma, tube glabrous except for ring of weak, descending hairs around mouth of tube; corolla lobes linear, ca. 10 x 0.7 mm, erect, joined at apex, margins only slightly recurved, abaxially green, adaxially blackpurple, margins densely lined with purplish (only basally whitish) trichomes, trichomes slightly vibratile, +1 mm long, somewhat moniliform in outline. Gynostegial corona in total +3.5 x 3.5 mm, cupshaped; staminal corona lobes connivent-erect, spathulate, abaxially slightly convex, adaxially slightly concave, 2-2.5 x 0.6-0.7 mm, glabrous, whitish NovoN 8: 38-40. 1998. This content downloaded from 207.46.13.77 on Mon, 23 May 2016 06:10:20 UTC All use subject to http://about.jstor.org/terms Volume 8, Number 1 1998 Meve & Masinde Ceropegia striata from Madagascar 39