eighty miles above the Cachivera de Cordova (near La 
Pedrera), but from Cordova to this point, Hevea Ben- 
thamiana predominates on the inundable banks. On the 
sandstone mesa at Araracuara, Hevea viridis var. towico- 
dendroides occurs, but not in abundance as at Chiribi- 
quete on the Apaporis. Below Cordova, the only species 
found along the banks is Hevea Benthamiana, with the 
exception of a small colony of HZ. pauciflora var. coriacea 
on and around the base of Cerro de LaPedrera. In the 
Miritiparana, Hevea Benthamiana is the only species 
found below the lowest rapids where the banks are sub- 
ject to heavy flooding. Above the rapids, Hevea guian- 
ensis var. lutea and H. guianensis are more abundant, 
except in certain localities (especially in several large 
igapos) where Hl. Benthamiana and H. pauciflora var. 
coriacea also occur in abundance in sandy catingas and on 
rocky elevations in the neighborhood of the numerous 
falls and rapids of the Miritiparana. In the hinterland of 
the upper reaches of the river, Hevea guianensis and its 
variety /utea are found to the exclusion of H. Bentham- 
jana but not of HI. pauciflora var. coriacea. 1 suspect 
that Hevea viridis also occurs in the Miritiparana, but no 
trees were encountered. 
Purumayo River Basin: The Putumayo, with its 
main affuents—the Caraparana and I garaparana—is per- 
haps the most uniform area of Colombia as far as the dis- 
tribution of Hevea is concerned. Hevea, as an important 
element of the flora, does not extend upstream in the 
Putumayo beyond Caucaya. From this point nearly to 
Arica, the chief representatives of the genus are Hevea 
guianensis and its variety lutea. Below Arica (or the 
mouth of the I[garaparana), H. Benthamiana begins to 
appear, and, near the Brazilian border and possibly also 
in the Rio Cotuhé, it predominates over the other two in 
[ 14 ] 
