Maguire, Bassett & Wurdack, John J. 1964. The botany of the Guayana Highland--Part V. Mem. New York Bot. Gard. 10: 1-278.
Melastomataceae
Latin Diagnosis - A speciebus 26-33 Monographiae Cogniauxii differt foliis planis supra et subtus modice stellato-puberulis pilis glandulosis sparsissime intermixtis. Frutex 1-2 m; ramuli teretes petiolis inflorescentiisque dense pilis stellatis sessilibus vel usque ad 2 mm stipitatis obsiti pilis glanduliferis ca. 0.3-0.5 mm longis sparse intermixtis. Folia in dimensionibus vix disparilia; petioli 1.5-4 cm; lamina 4.5-16 X 2.8-9 cm oblongo-ovata apice vix (ca. 0.5-1 cm) subabrupteque hebeti-acuminata basi vix (2-4 mm) cordata membranacea supra et subtus modice stellato-puberula pilis ad 0.15 mm stipitatis pilis glanduliferis 0.3-0.7 mm longis sparsissime intermixtis 7- vel sub-9-nervata nervis secundariis ca. 5-8 mm inter se distantibus nervulis non vel vix anastomosantibus ad margines remote crenulato-serrulata (dentibus ca. 2-3 mm inter se distantibus) et sparse patenti-ciliata ciliis caduce glanduliferis. Panicula ad 5 cm longa oblongo-pyramidata submultiflora; flores 5-meri sessiles vel ad 5 mm pedicellati; bracteolae ca. 0.5 mm longae lineares sparse stellato-furfuraceae ad hypanthii basim hisertae caducae. Hypanthium (ad torum) 3 X 2.5 mm dense stellato-puberulum pilis sessilibus vel vix (0.1 mm) stipitatis et apicem versus sparse glanduloso-setulosum; calycis tubus 1 mm altus, lobis interioribus 1.5 X 2.5 mm obverse ellipticis apice rotundatis extus dense et intus sparse stellato-puberulis, dentibus exterioribus ca. 0.5 mm eminentibus oblongis modice stellato-puberulis et extus sparse glanduloso-setulosis. Petala 4.5-5 X 3 mm obovato-oblonga apice vix emarginata. Stamina vix dimorphica; filamenta 2.9-3.3 mm longa; antherarum thecae 2.8-3 vel 1.8-2.2 mm lanceolatae vix curvatae convolutae basi rotundatae, connectivo non prolongato dorsaliter basi minute (0.1 mm) hebeti-mucronato. Stylus 6-6.5 X 0.4-0.15 mm; stigma punctiforme ; ovarium 4-loculare 2/3-3/4-inferum apice 0.5 mm liberum in collum 0.2 mm altum modice stellato-puberulum circum stylum protractum.
Type. Flowers white, occasional at forest edge on granitic laja on right bank of Rio Siapa 8 km below Raudal Gallineta (about 100 river km from mouth), Terr. Amazonas, Venezuela, alt. 130-300 m, 20 Jul 1959, J. J. Wurdack dc L. S. Adderley 43519 (holotype US 2342635).
All the suggested relatives of C. siapensis have upper leaf surfaces bullatestrigulose or densely strigose with non-stellate hairs; several species are obscurely stellulate-puberulous between the bullae. The anther shape of the Siapa species is like that of C. strigillosa (Sw.) DC. and its immediate relatives, rather than resembling that of the C. novemnervia species-group. I feel that the synonymization suggested by Gleason (Brittonia 1: 167. 1932) is excessive; at least C. pustulata D C . sensu Cogniaux and R. O. Williams is distinct from the C. novemnervia grouping (and perhaps only varietally distinct from C. strigillosa). C. pustulata is quite suggestive of C. siapensis, but has pustulate moderately glandular-setulose upper leaf surfaces, larger stellate hairs, densely glandularsetulose hypanthia, and ovary apices with glandular-setulose as well as stellulate hairs. C. pustulata stains the press sheets and to some extent the herbarium sheets yellow, indicating a chemical difference from the non-staining C. strigillosa. At least part of C. neglecta D o n sensu Gleason is actually C. pustidata; as noted by Macbride and indicated by the type photograph, the Madrid Ruiz & Pavon material purporting to be C. neglecta shows the interrupted-verticillate inflorescence spikes characteristic of C. capitellata (Bonpl.) Don, rather than the diffuse panicles of C. neglecta sensu R. 0. Williams. Central American material studied by Gleason as C. neglecta is mixed.