Monographs Details: Brachyotum quinquenerve var. pusillum Wurdack
Authority: Wurdack, John J. 1953. A revision of the genus Brachyotum (Tibouchineae-Melastomataceae). Mem. New York Bot. Gard. 8 (4): 343-407.
Description:Latin Diagnosis - Kypanthiorum ramulorumque trichomata laevia vel minutissime muriculata (sub lente 90x). Petioli 2-6(-9) mm. longi. Foliorum ramorum principium laminae 10-20 (raro ad 35) x 6-12 (raro ad 20) mm.
Distribution and Ecology - Distribution: northern Peru, alt. 2400-3200 m. Piura: Tadene between Provinces of Huancabamba and Jaen, Raimondi 2312 (USM). Cajamarca: northwest of Socota, Stork & Horton 10141 (F, G-DEL, UC); Cutervo, Raimondi 3841 (USM), Raimondi 4711 (USM); Llama, Sandeman 4163 (K). Amazonas: Yambrasbamba, Mathews 1257 (K); Chachapoyas, L. Williams 7572 (F, NY, US), Mathews 1258 (BM, K).
Type Collection and Locality: Pennell 15772 (HOLOTYPE PH); Peru, Dept. Amazonas, along Rio Sonche, west of Molinopampa, dry sandy barren, 2400 m. alt., 8 Jul. 1948. "Shrub. Petals anthracene violet."
B. quinquenerve is closely related on one hand to the complex including B.
huancavelicae and B. grisebacbii, on the other to B. campanulare. Its 5-7-nerved
leaves and usually well-developed paniculate inflorescences serve as distinctions
from the small-leaved Peruvian relatives. The McLean Chinchao specimen
cited here was placed by Triana and Cogniaux under B. campanulare, but has the
inflorescence and sepals of B. quinquenerve, although nearly smooth trichomes;
the label on this specimen states "Ex Herb, de R. and P. Lima" and the sprig is
matched exactly by a lanceolate-leaved sprig on the herb.Ruiz & Pavon Chinchao
sheet (F) and the Rivero collection (P), so probably this collection has been miscredited
The small foliage of var. pusillum gives it quite a different appearance from
var. quinquenerve; the inflorescences are also less well-developed than in the
typical variety. Unfortunately, no collections from areas between Cajamarca and
Huanuco have been seen, so the geographical disjunction, if any, and the variation between the varieties could not be established. The specimens of the typical
variety which have nearly smooth trichomes are otherwise well-marked by the
large leaves; the roughening of the hairs is most marked in the Cuzco collections.
Several sheets from Cuzco have gland-tipped trichomes on the hypanthium, sepals,
bracteoles, and pedicals: West 6422 p.p. (GH p.p.), Herrera 3208 p.p. (NY
p.p., F), and Cook & Gilbert 1171 (US). This has not been deemed worthy of any
formal recognition because of variation within a single collection and similar
glandulosity fluctuation in other species.
In addition to the specimens cited for B. quinquenerve t Raimondi 7238 (USM)
from Tambillo in Dept. Ayacucho should be considered. This collection has minutely
roughened hairs; elliptic, 3"nerved leaf blades, 12-21 x 5-7 mm.; and flowers
similar to B. quinquenerve. It may represent a distinct species or a variety of
B. quinquenerve. In habit, it is very suggestive of var. pusillum, except for the
3-nerved leaf blades and roughened hairs. The densely strigulose lower leaf surfaces,
ternate flowers, and glandularrciliate acute petals separate it from B. huancavelicae;
the much denser and roughened pubescence and glandular-ciliate
petals, from B. grisebachii.