I have by now studied 24 gatherings of this species, which apparently has a
wider distribution than D. laurifolia, being found at altitudes of from 500 to 2100
m in the Upper Mazaruni River region of the Pakaraima Mts. in British Guiana, in
Venezuela (on the tepuis of Estado Bolivar, apparently less common than D.
laurifolia; on the cerros of Territorio de Amazonas, evidently much more frequent
than D. laurifolia), and also in northwestern Amazonian Brazil and in Amazonian
Colombia where D. laurifolia has not yet been collected. As with D. laurifolia
there is remarkable variation in the size and shape of the leaflets, and in the size
of the calyx and capsule. Moreover, the species varies in habit, from a small
shrub of 3 ft to a forest tree 50-80 ft high with a trunk 1-11/2 ft in diameter.
Nevertheless, I am unable to distinguish any of the specimens even as a variety,
much less as a distinct species. Variation in the leaflets between individuals
from one small area is particularly well shown in the four collections from the
Cerro Sipapo (Paraque). Specimens from the eastern end of the range, in British
Guiana, have the largest and broadest leaflets, while those at the western end,
in Amazonian Colombia, have leaflets of the smallest and narrowest type. The
color of the corolla varies from lavender or light pink to white. In my account of
this family in Dr. Steyermark's "Contributions to the flora of Venezuela"* I
referred his Ptari-tepui' material to D. densicoma with some doubt, but the difficulty
of the calyx character is now cleared up by the numerous recent collections
from so many localities. The calyx is at first entire, and then splits bilaterally
into 2 or sometimes 3 broad lobes. At this stage the pressed calyx
sometimes appears spathaceously split down one side only. Later, the two broad
lobes become themselves deeply divided, so that eventually there are four subequal
lobes. When there are three original lobes, the third of these remains undivided
with the result that there are five subequal lobes at the final stage.
D. densicoma, which is presumably the ancestor of D. laurifolia, is always distinguished
from it by the pinnate leaves and by the relatively longer and narrower, less elliptic, capsule.