of buttressing is equally as constant in Micrandra Lopezii, 
for at least 175 individuals were examined in the two lo- 
calities known for the plant without our finding a single 
buttressed individual. Special attention was devoted to 
this study, since buttressing is such a fundamental char- 
acter in Micrandra. The rounded, thick nature of the 
buttresses of Micrandra Lopezi forma anteridifera is un- 
like that in any other concept of the genus. Buttresses 
in Micrandra are either usually rather thin and sharp, 
extending outwards from the trunk enormously (as in 
M. Spruceana) or becoming stilt-like (as in M. crassipes). 
The epithet anteridifera refers to the presence of buttress- 
roots on this form of Micrandra Lopezi. 
Our trip to the headwaters of the Rio Curicuriari was 
made expressly to study the representatives of Hevea 
and Micrandra in that most fascinating of rivers. We 
continued upstream as far as the Serra Cujubi, a small 
mountain located not far southeast of Serra Tukano, 
partly to ascertain if Micrandra Lopezu crossed over from 
the Uaupés to the Curicuriari drainage-area by way of 
‘these granitic hills and their attendant caatinga-forests. 
It is, I think, highly significant that the new species and 
its form should be so restricted to the Uaupés and upper 
Curicuriari. One whole year in the upper Rio Negro 
basin failed to uncover other localities for the M. Lopezi 
concept. ‘There can be little doubt but that other local- 
ities (the concept is always found in small, isolated colon- 
ies) do exist, but we may venture to say that they are 
not numerous and are not far from the focus comprised 
between the Uaupés and the Curicuriari. 
Micrandra Rossiana R. E. Schultes sp. nov. 
Arbor monoecia, usque ad septuaginta pedes alta 
(saepe multo minor), usque ad decem vel duodecim pol- 
lices in diametro; truncus erectus et columnaris, sine 
[ 211 ] 
