Murea Pires of the Instituto Agronomico do Norte of 
Belém, I had an opportunity of visiting the type locality 
of Hevea microphylla — the Uha de Xibari — and of 
studying a number of trees, from some of which collec- 
tions were made. 
Later, during my stay in the Rio Negro basin, I en- 
countered many hundreds of trees of Hevea microphylla 
at Piloto, near Barcellos, and along the Rio Negro, from 
a point slightly above the confluence of the Negro and 
the Uaupés to the mouth of the Icana, with an extraor- 
dinary concentration in the vicinity of the town of Sio 
Felipe, slightly below the mouth of the I¢ana. This spe- 
cies was also found to be present in surprising densities 
along the lower course of the Rio [cana and the Rio Nié. 
A botanically fascinating trip into the country of the Rio 
Dimiti, an affluent of the left bank of the upper Rio 
Negro which penetrates completely unknown territory, 
brought to light Hevea microphylla in this river. Farther 
upstream in the Rio Negro, Hevea microphylla was found 
to be rather abundant along the inundated banks of the 
lowermost course of the Rio Guainia, in both Colombian 
and Venezuelan territory. It was also collected in the 
Rio Curicuriari, although it is not at all common there. 
Along the low flood-banks of the Igarapé da Chuva at 
Tarecud on the Rio Uaupés and along the lower portion 
of the Rio Tiquié, an affluent entering the Uaupés be- 
low 'Taracud, Hevea microphylla forms one of the charac- 
teristic elements of the flora. In several other localities, 
especially on the islands in the Rio Uaupés and the mid- 
dle Rio Negro, reports of the inhabitants indicated the 
presence of Hevea microphylla. Their accurate descrip- 
tion of the fruit of this species, so different from that of 
all other Heveas, and the widely known common name 
of seringueira tambaqut, leave no doubt in my mind that 
these reports are reliable. 
[115 ] 
