We may, then, on the basis of the collections and these 
reports (which, in many cases, are from points interme- 
diate between the localities from which collections have 
been made), state that Hevea microphylla is endemic to 
the Rio Negro basin, ranging continuously, when eco- 
logical conditions will permit, from slightly below Bar- 
cellos up the Rio Negro to the confluence of the Casi- 
quiare and the Rio Guainia nearly to Maroa; possibly 
into the Casiquiare; in the lower reaches of most of the 
affuents of the middle and upper portions of the Rio 
Negro, such as the Icana, Nié, Dimiti, Curicuriari, Pa- 
dauri, Enuixi and Caurés; up the Rio Uaupés, especially 
on the islands, to Ipanoré (the first major rapids going 
upstream), possibly not beyond this point; and in the 
lowermost reaches of the affluents of the Uaupés. Form- 
erly believed to be confined to Brazil, Hevea microphylla 
has now been found in both Colombian and Venezuelan 
territory. 
Descriprions OF HEVEA MICROPHYLLA 
Hevea microphylla Ule in Engler Bot. Jahrb. 35 
(1905) 669, tab. 1: fig. j, k, 1, m; Ule in Kautschuk- 
gewinnung (Kolonialwirtsch, Kom. 1905) (1905) 10; 
Huber in Bol. Mus. Goeldi 4 (1906) 684 [non accurate, 
sub Hevea minore], 6836; Pax in Engler Pflanzenr. 4, 
147 (1910) 125; Ducke in Arch. Inst. Biol. Veget. 2, 
no. 2 (1985) 241, pro parte, tab. p. 246, a-f, 247, a-b 
[non accurate, sub Hevea minore|; Ducke in Bol. Técen. 
Inst. Agron. Norte, no. 10 (1946) 20, pro parte; Schultes 
in Bot. Mus. Leafl. Harvard Univ. 18 (1947) 1-9; Sei- 
bert in Ann. Mo. Bot. Gard. 84 (1947) 276, 285, 292, 
pl. 89; pl. 40, fig. 8; pl. 41, fig. 8; pl. 42, fig. 8; pl. 43, 
fig. 2. 
Hevea microphylla Ule var. typica Pax in Engler 
Pflanzenr. 4, 147 (1910) 126. 
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