mal seed of Hevea guianensis var. lutea and that of Hi. 
rigidifola, especially in shape and in coloration. The 
seed of the former is, however, smaller than that of the 
latter. This similarity may be significant, but we cannot 
draw any definite conclusions on the basis of the few 
known seeds of Hevea rigidifolia. 
The flower of Hevea rigidifolia does indeed show, in 
several characters, an approach to that of H. gwianensis 
var. /utea; this was suggested by Spruce in the original 
description when he stated: ‘‘antherae JS. /uteae.”” None 
of the floral characters, however, indicates any degree of 
close affinity. Moreover, the habits and habitats, and 
therefore probably also the history, of the two concepts 
are very unlike in all respects, for the one is a widely 
distributed forest giant growing on well-drained ground 
along the banks of rivulets or brooks, whereas the other, 
apparently a highly restricted endemic, is usually a small 
tree of xerophytic caatingas. 
In floral characters, Hevea rigidifolia does, as Ducke 
has pointed out, resemble H. Benthamiana very closely. 
In Hevea rigidifolia the staminate buds are extremely 
acuminate and cylindric-conic; in. H. Benthamiana they 
are commonly acuminate, although the latter does not 
have the segments apically spirally twisted as does the 
former. Although the flowers of the former are much 
larger than those of the latter, the general form of the 
urceolus of the staminate flower is markedly similar. 
There are, however, several rather important differences 
which do serve to separate the two. In Hevea rigidifolia 
the number of anthers, surprisingly constant, is very low 
(normally only six), the suprastaminal column is conspic- 
uously slender and elongate, and the ovary is completely 
glabrous; whereas, in H. Benthamiana, the anther num- 
ber is variable (usually from six to nine), the column is 
short, and the ovary is densely white-sericeous. In both 
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