Macrocentrum gracile Wurdack
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Authority
Maguire, Bassett & Wurdack, John J. 1958. The botany of the Guayana Highland--Part III. Mem. New York Bot. Gard. 10: 1-156.
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Family
Melastomataceae
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Scientific Name
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Description
Latin Diagnosis - M. fruticoso Gleason affinis sed foliis maioribus et tenuioribus basi distincte eordatis pedicellis longioribus petalis minoribus conneetivo antherarum dorsali minore. Plantae herbaceae suberectae, caulibus ad 30 cm longis, quadratis vel sub-4-alatis glabris. Folis opposita in quoque juyo aequalia vel subaequalia; petiolus 2.8 cm, glaber; lamina tenuissima 4-12 X 3-7 cm, ovata vel oblongo-ovata, apice breviter (ca. 1 cm) hebetiacuminata, basi breviter (ad 1 cm) cordata lobis basilaribus plerumque imbricatis, 5-7-nervia nervis primariis gracilibus secundariis indistinctis, ad marginem integra vel vix dentieulata ciliata ciliis patentibus ca. 1-2 mm longis et 1-2 mm inter se distantibus, supra sparse strigosa pilis gracilibus 1-2 mm longis 0.5-3 mm2, subtus in superficie venisque primariis glabra in venulis (praecipue marginem versus) sparsissime strigulosa. Inflorescentia laxa glabra pedunculo gracili 6-8 cm longo ramis primariis umbellatis plerumque 2-3 usque 4 cm longis, ramulis umbellatis 3 vel 4 in quoque ramo 1-3 cm longis 2-4-floris. Flores secundi 4-meri glabri; pedk-elli graciles, 5-10 mm. longi. Hypanthium 3 X 1-2 mm; calyx vix (0.1-0.2 mm) coalitus, lobis 0.4 X 0.9 mm late triangularibus obtusis extus cum dente 0.4 mm longo vix (0.2 mm) projecto armatis. Petala 3.6 X 1.4 mm anguste obovata aeuta. Stamina isomorphica; filamenta 1.8 mm longa; antherae loculi 2.5 mm longi, apice attenuati, conneetivo sub loculis ad insertionem filamenti non producto sub filamento dorsaliter in eaudam 0.4 X 0.1 mm hebeti-acutam producto. Ovarium biloculare; stylus 4.5 X 0.1 mm; stigma punctiforme; semina 0.28 X 0.2 mm, ovoidea unilateraliter truncata minute tuberculata.
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Discussion
Figure 12, c.
Type: delicate annual with white flowers, infrequent under overhanging rocks on summit of southeast-facing escarpment, elev. 700 m, Mt. Ebeni, British Guiana, Oet 15, 1951, Bassett Maguire 32117 (NY).
M. fruticosum has smaller thicker leaf-blades with usually truncate bases, pedicels only 1-3 mm long, petals 7-7.5 mm long, and larger anthers with relatively longer dorsal appendage.