Macrocentrum anfractum Wurdack
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Authority
Maguire, Bassett & Wurdack, John J. 1964. The botany of the Guayana Highland--Part V. Mem. New York Bot. Gard. 10: 1-278.
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Family
Melastomataceae
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Scientific Name
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Description
Latin Diagnosis - M. gesneriaceo Sandw. et M. minori Gleason affinis sed petalis apice glanduloso-setosis. Herba 5-12 cm alta vix decumbens vel adseendens ubique glandulis sessilibus primum rubris demum nigrescentibus sparse obsita; caulis gracilis anfractus quadrangulatus ad angulos sparse glanduloso-setulosus pilis ad 1 mm longis vix adscendentibus. Folia ut videtur alterna unum paris inconspicuum abortivum appressum glanduloso-setulosum 0.5-1 mm longum in nodis alternans; folia evolnta cum petiolo glabro 1-2 mm longo, lamina 1.3-3.5 X 0.5-0.7 mm lanceolata apice anguste acuta basi acuta tenuiter membranacea uninervata nervis lateralibus aegre evolutis supra pilis inframarginalibus interdum glanduliferis exceptis glabra subtus in superficie centrali glabra vel sparsissime glanduloso-strigulosa marginem versus sparse glanduloso-strigulosa ubique modice elliptico-punctata punctis ca. 0.3 mm longis primum albidis demum nigrescentibus ad margines incurvo-ciliolata pilis ca. 1 mm longis interdum glanduliferis. Flores 4-meri in foliorum abortivorum superiorum axillis solitarii vel bini primum terminales demum laterales; pedicelli ca. 1 mm longi. Hypanthium calycis tubum includens 3 mm longum apicem versus (circum torum) sparse glanduloso-setulosum; calycis lobi 1x1.5 mm obverse elliptici apice rotundati extus sparse glanduloso-setulosi et infra apicem minute unituberculati ad margines dense cum glandulis sessilibus obsiti. Petala ca. 6 mm longa apice setula unica glandulifera ca. 0.4 mm longa armata. Filamenta ca. 3 mm longa; antherarum thecae ca. 2 mm longae, appendice dorsali descendente ca. 0.8 mm longa. Stylus ca. 5 X 0.2 mm; stigma truncatum; ovarium non visum; fructus pedicellum indistinctum includens 6-7 mm longus; capsula trilocularis apice trigona et vix exsculpta.
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Discussion
Type. Leaves green above, below bright red with white margin and midrib, seen only once on wet mossy rock at Porkknocker Camp 2 on Partang River about 19 k m above mouth, upper Mazaruni River basin, Pakaraima Mts., British Guiana, alt. 625 m, 28 Jun 1960, Stephen S. Tillett, Carolyn L. Tillett, & Rufas Boyan 43929 (holotype NY; isotype US).
All floral measurements were taken dry, the one flower of the collection not being dissected. The sympodial zigzagging of the upper stem is more pronounced in M . anfractum than in its near relatives, the angles formed being about 125°-140°. M . anfractum seems intermediate between M . gesneriaceum and M . minus, having the pseudo-alternate leaves of the former and the gland-tipped cauline hairs of the latter; it approaches M. gesneriaceum (with elliptic to oblong-elliptic leaves) closer in foliage. Both relatives have esetulose petals.