A Second Species of the Malagasy Genus Secamonopsis (Asclepiadaceae)

Abstract

Secamonopsis microphylla sp. nov., from dry southern Madagascar, is described, illustrated, and compared to S. madagascariensis Jumelle, the only other known species of this genus. While preparing a treatment of the tribe Secamoneae (Asclepiadaceae) for the Flore de Madagascar et des Comores, and during the course of a survey of the pollen structure within this tribe, a new species, Secamonopsis microphylla, was encountered. This adds a second species to the hitherto monotypic Malagasy genus Secamonopsis Jumelle. Secamonopsis microphylla Civeyrel & Klackenberg, sp. nov. TYPE: Madagascar. Toliara Prov.: 17 km E of Toliara on Road No. 7, E of Montagne de la Table, alt. 110 m, 20 Nov. 1994, Civeyrel 1242 (holotype, P; isotypes, K, S, TAN). Figure 1. Species haec a Secamonopsi madagascariensi habitu fruticoso, brachyblastis foliiferis, inflorescentiis 1-3 floribus et foliis minoribus differt. Shrub, prostrate or erect, up to 1.5 m tall, with young branches + densely covered by short appressed hairs, glabrescent. Leaves mostly on opposite brachyblasts, grayish green with reddish margin; blade 5-10 x 2-3 mm, oblong to narrowly obovate, tapering at base into a distinct petiole, usually rounded but sometimes acute or truncate at the apex, with sparse to rather dense short appressed hairs on both sides, sparser above, with even margin; venation with only midrib visible; epidermal cells of lower leaf surface tuberculate-papillate; petiole 1-2 mm long, with appressed hairs. Flowers pentamerous, actinomorphic, usually solitary but sometimes 2-3 on the brachyblasts; pedicels 1-2 mm long; bracts 2 or 3, 1-3 mm long. Calyx lobes free, 1.8-2.4 x 1.5-2.0 mm, concave, longer than the corolla tube, obovate to + circular, rounded at the apex, hairy outside and along the margin, glabrous inside, without colleters. Corolla imbricate, with lobes fused for ca. 2/5 of their length into a tube, yellow; tube 0.9-1.2 mm long, with long white retrorse hairs in upside down Vs with 5 bunches of erecto-patent hairs at the top below the lobe sinuses; lobes 1.5-1.7 x 1.2-1.4 mm, oblong, rounded at the apex, thick, glabrous. Stamens inserted at base of corolla tube; staminal column 0.60.8 mm long; filaments with horny margins distinctly projecting at base; thecae papillately hairy at the top. Coronal lobes inserted along lower half of anthers, 0.3-0.5 mm long, dorsiventrally compressed, + as broad as long, rounded at the apex, straight, much shorter than the staminal column, glabrous. Pollinia seemingly 2 per corpusculum but in fact 4 glued together in pairs, ca. 0.1 mm long, + ascending, lens-shaped to ellipsoid, attached to 2 narrow distinct caudicles on an ellipsoid soft corpusculum. Stigma head slightly projecting above the staminal column; narrower upper part ca. 0.4 mm long, slightly bifid at the apex. Follicles usually paired, ca. 4 x 0.5 cm, narrowly ovoid, glabrous, horizontal. Seeds ca. 5 mm long; hairs 7-15 mm long. Secamonopsis microphylla is sympatric with the hitherto only known species of Secamonopsis, S. madagascariensis Jumelle (1908: 6), but seems to be restricted to calcareous soil with rather sparse shrub vegetation while S. madagascariensis is usually found in gneissic areas. It is distributed in the dry southwestern part of Madagascar and has not been found outside the Southern Domain phytogeographical area (after Humbert, 1955). Flowering November to March. Secamonopsis microphylla clearly belongs to the genus Secamonopsis, although it differs considerably in habit from S. madagascariensis. It has the same structure of the gynostegium and the characteristic pollinaria as in S. madagascariensis. The NovoN 6: 144-146. 1996. This content downloaded from 207.46.13.111 on Tue, 09 Aug 2016 05:30:28 UTC All use subject to http://about.jstor.org/terms Volume 6, Number 2 1996 Civeyrel & Klackenberg Secamonopsis microphylla 145