New taxa and a new rank of Selaginella (Selaginellaceae) from Madagascar and the Comoros

Two new species of Selaginella from Madagascar, S. bemarahensis and S. marinii, are described and illustrated, as are a new subspecies of S. nivea Alston and a new form of S. fissidentoides (Hooker & Greville) Spring var. fissidentoides. The Malagasy species S. fissidentoides is segregated into two varieties, one of which has been previously known as S. amphirrhizos A. Braun ex Hieronymus. The taxonomic position and closest relationships of each taxon are briefly discussed. The monogeneric family Selaginellaceae comprises about 700 species distributed throughout the world, but for the most part concentrated in tropical and subtropical areas. The most recent infrageneric classification of the genus Selaginella (Jermy, 1986) recognized five subgenera. The last complete account of the family in Madagascar and the Comoros was made by A. H. G. Alston (1932), who listed eleven species of Selaginella as occurring in that area. Two additional Malagasy species were established, one by R. M. Tryon (1955) and one by W. Rauh and W. Hagemann (1991). During revision of this family for the Flore de Madagascar et des Comores, made possible by increased collecting in the last 40 years (specimens have been studied from B, BM, K, P), one existing taxon has been divided and four distinct taxa have been noted. They are described in this paper, so that the names can be used in the Flora treatment. Two species, S. bemarahensis and S. marinii, belong to the subgenus Heterostachys Baker, and one subspecies, S. nivea subsp. humbertii, to the subgenus Tetragonostachys Jermy. Selaginella fissidentoides var. amphirrhizos and S. Jissidentoides fo. ovata (of var. fissidentoides) belong to the subgenus Stachygynandrum (P. Beauvois) Baker. At present, fifteen species of Selaginella are recognized in Madagascar and the Comoros, one of them represented by two subspecies and one by two varieties and one form. The descriptive terms referring to shape, surface, and structure of spores follow terminology used by A. F. Tryon and B. Lugardon (1991). 1. Selaginella bemarahensis S. Stefanovid & Rakotondrainibe, sp. nov. TYPE: Madagascar. Mahajanga: Reserve Naturelle de Bemaraha, au sud-est d'Antsalova, 18?45'S, 44?48'E, 400 m, 23 Aug. 1987, Phillipson 2257 (holotype, P; isotype, MO not seen). Figure 1A, B. Species haec, inter species subgeneris Heterostachys Baker, habitu parvulo et muscoso ad S. perpusillam Baker accedens, sed foliis lateralibus et medianis similaribus (praeter staturam), foliorum mediorum apice acuto et foliorum lateralium marginibus et sporophyllorum ventralium denticulatis (non ciliatis) ab ea differt. Plants tiny, moss-like, slender, without rhizome, forming mats. Main stem suberect to erect, 2-4.5 cm long, outline lanceolate, rarely or not branched, provided with rhizophores. Branches, when present, short and unbranched. Rhizophores dorsal, situated on the lower half of the stem, 2-8 mm long and very fine, straw-yellow, dichotomizing 2-3 times. Leaves dimorphic, pale green, herbaceous, widely spaced on the main stem, contiguous toward the tips of the main stem and branches. Lateral leaves subequal, lanceolate, 1.8-3 mm long, 0.6-1 mm wide, midrib apparent, base symmetrical and blunt, apex acute, margin subentire to denticulate all around the leaf. Axillary leaves similar to lateral but equal. Median leaves also similar to lateral leaves but smaller, 1.2-1.8 mm long, 0.5-0.8 mm wide. Strobili solitary, inserted terminally on main stem and branch tips, bilateral, resupinate, 5-8 mm long and 1.5-2 mm wide. Sporophylls dimorphic, spreading, margins denticulate. Dorsal sporophylls ovate-lanceolate, 1-1.5 mm long and 0.4-0.6 mm wide, keeled, keel well developed and denticulate, base blunt, apex acute. Ventral sporophylls ovate, 0.9-1.1 mm long and 0.4-0.6 mm wide, slightly or not keeled, base blunt, apex acute-acuminate. Megaspores light lemon yellow, 278-287 C.m diam., spherical, trilete, with laesura nearly equaling the radius, surface finely tuberculate on both proximal and distal face (Fig. 2A). Microspores bright orange, 35-38 /m diam., tetrahedral-globose, trilete, with laesura nearly equaling the radius, surface laevigate to finely granulate on both proximal and NovoN 6: 203-209. 1996. This content downloaded from 207.46.13.72 on Sun, 07 Aug 2016 07:12:16 UTC All use subject to http://about.jstor.org/terms