Monographs Details: Miconia dioica Wurdack
Authority: Maguire, Bassett & Wurdack, John J. 1964. The botany of the Guayana Highland--Part V. Mem. New York Bot. Gard. 10: 1-278.
Family:Melastomataceae
Scientific Name:Miconia dioica Wurdack
Description:Latin Diagnosis - Sect. Cremanium. M . manicatae Cogn. & Gl. ex Gl. affinis sed foliis ovatis non ciliatis, ramis ad nodos in petioli insertionem elevatis non vere manicatis, floribus minoribus. Frutex scandens ad 5 m altus glaber; ramuli primum rotundato-quadrangulares demum teretes ad petioli insertionem in cylindrum 1-2 mm longum elevati. Petioli 1-2 cm; lamina 4-8 X 2-4.5 cm lanceolata vel ovata apice per 0.5-1 cm subgraditer hebeti-acuminata basi rotundata tenuiter coriacea leviter (1-2 mm) triplinervata (jugo exteriore tenuissimo neglecto) nervis secundariis 1-3 mm inter se distantibus nervulis laxe reticulatis subtus primum modice nigropunctata punctis demum inconspicuis integra non ciliata. Panicula 4-8 cm longa pyramidata ramis primariis secundariisque rectis vel vix adscendentibus; flores 5-meri ut videtur dioici ca. 1 mm pedicellati, pedicellis ad medium bibracteolatis; bracteolae 0.7-1 mm longae oblongo-subulatae caducae. Hypanthium (ad torum) 0.9-1 X 0.9 mm; calycis tubus 0.05-0.1 mm altus, lobis interioribus ca. 0.15 mm longis remotis dentes exteriores tuberculatos aequantibus. Petala 0.7-0.75 X 0.7-0.9 mm rotundata apice vix retusa basi ca. 0.15 mm unguiculata apicem versus ad margines vix erosula glabra. Stamina isomorphica. Flores masculini: filamenta 1 mm longa; antherarum thecae 0.5 X 0.35 mm obovatae apice truncatae et late biporosae basim versus intus biseptatae, connectivo basi 0.1 mm prolongato incrassato non lobulato; ovarium abortivum non ovulatum, stylo 0.2 mm longo incluso, stigmate punctiforme. Flores feminini: stamina abortiva, filamentis 0.8 mm longis, antherarum thecis 0.2 mm longis late biporosis, connectivo 0.15 mm prolongato incrassato; stylus 1.5 X 0.3 mm ca. 1.2 mm e hypanthio eminens; stigma capitellatum 0.6 mm diam; ovarium 3-loculare multispermum 2/3-inferum glabrum apice in conum 0.2 mm altum elevatum; semina 0.6 X 0.4 mm minutissime tuberculata.

Discussion:

Type. Inflorescence branches and hypanthium red-tinged, petals and stamens white, locally frequent on dry side of middle falls of Rio Tirica below Summit Camp, Chimanta Massif, Edo. Bolivar, Venezuela, alt. 1760 m, 1 Mar 1955, J. A. Steyermark & J. J. Wurdack 1226 (holotype U S 2342416). Paratypes. VENEZUELA, Edo. Bolivar. Chimanta Massif: upper slopes of Apacara-tepui, alt. 1700-1850 m, Steyermark 75829; Torono-tepui, alt. 1895-1910 m, Steyermark & Wurdack 1074; Agparaman-tepui, alt. 1880-1955 m, Steyermark & Wurdack 1129.Heterostyly has long been suspected in the minute-flowered Andean species of Miconia Sect. Cremanium, but the inconspicuous (described) morphologic differences and lack of field observations have prevented acknowledgment of this phenomenon. In M. dioica, there seems no doubt as to heterostyly and, judging by the individual collections, dioecism; the type collection is male, Steyermark 75829 is fruiting, and the other two paratypes are female flowering and fruiting. M. manicata, from the Colombian Andes, has elliptic ciliolate leaf blades, manicate branchlet nodes but with petioles simply inserted on the stems above the nodal elevation, and somewhat larger flowers (petals 1.8 mm long and anthers 1.3 mm long); the anthers are basally 4-celled as in the Guayana species. In Cogniaux' monograph, M. dioica would key to M. tinifolia Naud. or M . pinetorum Naud., both of which have larger flowers and lack elevated cauline nodes. Jamaican material of M. rubens (Sw.) Naud. (Nichols 108, Eggers 3622) shows a very slight tendency towards nodal development and perhaps dioecism (or surely heterostyly), but has oblong-elliptic serrulate leaf blades. In general habit, M. dioica resembles M. sarmentosa Cogn. of French and Dutch Guiana.

M. rupestris Ule was described as with 2-pored anthers; however all recent material from Roraima, Ilu-tepui, the Chimanta Massif, and Auyan-tepui, agreeing with Ule's and Gleason's descriptions and the type photographs in minute details (quadrangular stems, with caducous spinules), shows 4-pored anthers. Apart from the purported 2-pored anthers, all of the features of M. rupestris maybe found within the many varieties of M. theaezans (Bonpl.) Cogn. (cf. var. subtriplinervia Cogn., var. tetragona Cogn., var triplinervia Cogn.); accordingly, I have referred nine collections from the four Venezuelan tepuis to M. theaezans. As for material from Roraima and Ptari-tepui ascribed to M. tinifolia Naud., I feel sure that it is at least subspecifically distinct from Andean collections but am deferring any adjustment until the Andean population is studied in detail. A recent collection from Cerro Yutaje (Maguire & Maguire 35329), fruiting only seems also involved in the M. theaezans-M. tinifolia problem, having distinctly 5-nerved cordulate leaf blades; flowering material is required to establish firm identity of the Yutaje shrub.