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Systematics of the Amphi-Atlantic Bambusoid Genus Streptogyna (Poaceae)

1987; Missouri Botanical Garden; Volume: 74; Issue: 4 Linguagem: Inglês

10.2307/2399454

2162-4372

Thomas R. Soderstrom, Emmet J. Judziewicz,

Tree Root and Stability Studies

Streptogyna is the only herbaceous bamboo genus with an amphi-Atlantic distribution.Streplogyna chnita occurs in tropical Africa, Sri Lanka, and India, and S. americana is found throughout the Neotropics.Although marked differences in habit and in morphology of lodicules and starch grains suggest segregation at the generic level, they arc here retained in a single genus because they are quite similar in spikelet morphology and leaf anatomy.Multicellular microhairs are present on the lodicules of 5. crinita and mark the first report of microhairs in the genus.Multicellular microhairs are otherwise well developed in the grasses only in the African herbaceous bamboo Guaduella, and they may be a primitive feature in the family as they are common in its putative outgroup, the Joinvilleaceae.Streptogyna shows strong bambusoid affinities in its ligule and leaf anatomy, spikelet structure, caryopsis and embryo morphology, and chromosome number, but differs from the core group of the subfamily in its seedling morphology and lack of epidermal papillae.Autapomorphies in the two species suggest that neither could have been derived directly from the other.The grass genus Streptogyna was first brought voize, 1986).In a treatment of the herbaceous to the attention of Western botanists in the late bamboos of Sri Lanka, Soderstrom et al. (1987) 18th century, when British and Swedish coUec-offered a detailed descriptive account of the leaftors brought back specimens of "rat-catching bladeanatomyin the two taxa.The present study West Africa.A gath-provides a revision of the genus and attempts to ering from Nigeria by Palisot de Beauvois was clarify the relationships of the two species by Streptogyna examining characters that have not yet been he based on the only species known to him, S. studied in detail, such as morphology of lodicrinita.The narrow leaves and many-flowered cules, starch grains, and embryos, spikelets of Streptogyna were long taken as indications of pooid (festucoki) affinities.Thus Materials and Methods Bentham (1883), Hackel (1887), andHubbard (1936) all considered that the proper disposition Specimens of Streptogyma were examined from of this genus from the tropical rainforest lay with the following herbaria: AAU, B, BM, BR, CAY, this large, temperate-region grass group.But there CEPEC, F, G, ISC, K, M, MO, NA, NY, P, PDA, were dissenters, and Nees von Esenbeck (1835) RB, S, US, W, and WIS.For anatomical studies, and Steudel (1855), for example, suspected the spikelets, leaves, and embryos (Table 1) were bambusoid affinities of the genus.Streptogyna dehydrated in dimethoxypropane, infiltrated with was briefly revised by Hubbard (1956), who in-tertiary butanol, embedded in wax, sectioned usdicated that the group deserved tribal status, but ing a rotary microtome, and stained in chlorazol it was not until Tateoka (1958a) and Metcalfe black E. Lodicules were rehydrated with Aerosol-( 1 960) examined its leaf anatomy that the bam-OT before examination.Starch grains from carybusoid affinities of Streptogyna became clear, opses were cut on a freezing microtome and Recent workers agree that Streptogyna should be stained with I^KI.Observations of living plants placed in its own tribe in the Bambusoideae of^/r^/^/^^^^^na were made by Soderstrom in Bra-(Calder6n & Soderstrom, 1980; Clayton & Ren-(March 1972, and