final decision and before the preparation of a critical tax- 
onomic treatment. 
Even in the case of a number of easily accessible locali- 
ties in eastern Colombia, we are at a disadvantage because 
the herbarium material which is available is sterile. The 
very short flowering and fruiting seasons of Hevea make 
it impossible to gather complete material over a wide 
area in the same year. Sterile material, while better than 
no material, has very definite limitations as to its value 
in taxonomic work on Hevea. One example of the handi- 
‘aps imposed by incomplete specimens may be presented. 
In the gigantic crevasses and faults in one of the gro- 
tesque sandstone mountains near the confluence of the 
Ajaju and Macaya Rivers in the upper Apaporis basin, 
there exists a curious colony of very tall trees represent- 
ing apparently an undescribed variety of Hevea guianen- 
sis. It has excellent bark characters as well as peculiarities 
in leaf pilosity. Unfortunately, however, only very im- 
mature capsules could be obtained. Nothing is known of 
the seeds or flowers. This highly interesting tree, grow- 
ing under conditions of psammophytic and physiological 
drought some 600 to 800 feet above the surrounding 
forest floor or about 1600 feet above sea-level, may prove 
to be an important link in our understanding of the dis- 
tribution or even of the phylogenetic interrelationships 
of the Hevea guianensis-complex.* 
These considerations serve merely to emphasize the 
need for continued and systematically planned Hevea 
*This highland tree appears to have a number of striking similar- 
ities with the highland representatives of the Hevea guianensis-complex 
which I have recently had occasion to examine in the forests on the 
slopes along the upper Huallaga River in Peru. It is very evident that 
the greatest need at the moment is for more detailed taxonomic and 
distributional studies of the poorly understood species and varieties of 
Hevea in highland regions. 
[ 4] 
