apparently the earliest recognition of this distinct con- 
cept, antedating Hemsley (Hevea confusa) and Ducke 
(A. pauciflora var. coriacea) by many years (cf. Schultes 
in Bot. Mus. Leafl. Harvard Univ. 15 (1952) 264. 
Hevea rigidifolia (Spruce ev Benth.) Mueller- 
Argoviensis in Linnaea 34 (1865) 2038. 
Cotomsia: Comisaria del Vaupés, Rio Guainia basin, Rio Naquieni, 
at base of Cerro Monachi. Caatinga forest. June 1948, Richard Evans 
Schultes & Francisco Lopez 10112; Same locality and date. Schultes & 
Lopez 10118, 10119, 10120, 10122, 10130. 
This most unusual species of AZevea, recently redis- 
covered after the passing of a century (cf. Schultes in 
Bot. Mus. Leafl. Harvard Univ. 18 (1948) 97), has hith- 
erto been thought to occur only in Brazilian territory. 
It was naturally to be expected in adjacent regions of 
Colombia and was so indicated in an enumeration of spe- 
cies of Hevea in Colombia in 1945 (Schultes in Bot. 
Mus. Leafl. Harvard Univ. 12 (1945) 11). 
Recent explorations in the upper Rio Negro basin in- 
dicate that Hevea rigidifolia is rather widespread in a 
number of the affluent rivers of the right bank from the 
Rio Curicuriari northwards. It is extremely abundant in 
many of the caatingas of this region. Phytogeographi- 
‘ally most noteworthy was the discovery of the species 
far upstream in the basin of the Rio Guainia, at the base 
of the Cerro Monachi mass, in Colombian territory. The 
proximity of this locality to Venezuela would suggest 
the strong possibility that Hevea rigidifolia may also 
form a component of the caatinga forests of the Vene- 
zuelan Territorio del Amazonas. The discovery of Hevea 
rigidifola in Venezuela would indeed be significant, as 
most of the waters drain into the upper Orinoco system 
instead of the Amazon. 
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