guianensis. We have both encountered variability in the 
characters which have been used to maintain HZ. /utea as 
aspecies. In 1943 (Arquiv. Serv. Florest. Rio Janeiro 2 
(1943) 81) Ducke stated: ‘‘Quanto as relacdes de afini- 
dade entre as especies guranensis e lutea, e a descoberta 
de uma forma que parece representar uma transicaio de 
guianensis var. occidentalis para lutea var. pilosula.”’ 
Hans G. Sorenson likewise believes, after very extensive 
field work in the Amazon Valley, that H./utea represents 
but a variety of Hevea guianensis. 
Hevea guianensis and H. guianensis var. lutea occur 
most commonly on ‘‘tierra firme’” and on higher and 
well-drained knolls or river banks. They comprise the 
most widespread complex of Colombian representatives 
of Hevea. Furthermore, they occur coexistantly and are 
extremely abundant where the annual inundation does 
not exert a direct flooding or ‘‘drowning”’ influence for 
long periods. Of the two, Hevea guianensis var. lutea is 
by far the more abundant in most regions. Both are 
known generally as “‘siringa amarilla’’ because they have 
yellowish latexes; in regions bordering Brazil, the name 
‘*borracha fraca’’ is current. In Leticia, the Peruvian 
term ‘‘jebe debil’” is used. While these trees yield a 
weak rubber in some regions, the rubber from the Vau- 
pés, which comes for the most part from Hevea guian- 
ensis var. lutea, is considered to be good. There are 
numerous localized varieties and forms of both concepts. 
Hevea pauciflora (Spruce ex Benth.) Muell.-Arg. 
rar. COriacea Ducke in Arch. Inst. Biol. Veg. Rio 
Janeiro 2 (1935) 239. 
Hevea pauciflora var. coriacea, a small to medium- 
sized tree, occurs in light (catinga-type) forests on the 
slopes of rocky hills or in the vicinity of rock outcrops. 
It is not common in Colombia. The latex is whitish. 
This species is never tapped. 
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