Type Collection and Locality: Pennell 25857 (HOLOTYPE PH); Peru, Dept. Amazonas, Cerro de Fraijaco (Huaui-Huni) northeast of Tambo de Ventilla, in dry sandy soil, alt. 3000-3200 m., 7 Jul. 1948. "Shrub. Hypanthium and calyx jasperred; petals black." Known only from the type collection.
Cogniaux described this species as 4-merous; on the holotype fragment examined,
however, 6 of the 7 flowers were 5-merous; on the Kew isotype, all 15
examinable flowers were 4-merous. The leaf tubercles on the holotype fragment
are somewhat more prominent than usual, but the variation in development of these
hairs is quite great on the other collections. Among these other collections, except
for Matbews 47H, all of the 81 examinable flowers were 4-merous. However,
in Matbews 47H, half of the 16 examinable flowers were 4-merous, half 5-merous;
this collection also has leaves with the length/width ratio greater than usual in
the typical variety, narrower more acute sepals, and smaller connective prolongation
(0.7-0.9 mm., free of anther 0.3 mm.). Perhaps the holotype fragment and
Mathews 47H are hybridal variants (xB. angustifolium ?).
Both varieties of B. maximowiczii are in appearance quite distinct from B.
radula, the typical variety because of the smaller leaves, var. longifolium because
of the leaf blade length/width ratio of 2.6-3.3 [rather than 1.5-2(-2.4)].The
lower leaf surface reticulation is also much less obvious (or completely hidden in
var. longifolium) than in B. radula.