EXPLANATION OF THE [ILLUSTRATION 
Prare IV. A view of the caatinga at Taracuad, Rio 
Uaupés, Brazil, showing the abundance of Hevea 
rigidifolia (slender, columnar trees without buttress 
roots in center and background), These trees were 
tapped for rubber, the analysis of which is reported 
in the present article. 
Photograph by Ricuarp Evans Scuunres 
