combine with other general similarities in vegetative 
characters to indicate a rather close relationship with its 
companion of the caatingas, AZ. pauciflora var. coriacea. 
It is worth pointing out, incidentally, that while coria- 
ceous leaflets are very possibly a manifestation of xero- 
phytic caatinga conditions in both of these species, as in 
many other plants, there are sufficient similarities in 
vegetative characters to indicate that this is due to some 
affinity and not to an ecological parallelism between 
Hevea rigidifoha and H. pauciflora var. coriacea. 
The seed of Hevea rigidifoha does not appear to be 
similar to that of AZ. pauciflora var. coriacea. It is larger, 
broader in relation to its length, and much less sharply 
angular. However, one seed preserved with the collec- 
tion Mrées 21253 curiously approaches the shape and size 
which, so far as we know, is usual for Hevea pauciflora 
var. coriacea, being smaller, narrower, and very sharply 
angular in cross section. (This seed may have been in- 
cluded erroneously in F’rdes 21253, because it does not 
match any other seeds in the same collection. Further- 
more, rdes 21253 was growing in close proximity to 
Froes 21249 which appears to be referable to the Hevea 
pauciflora var. coriacea complex, and a confusion as to 
the source of this seed would not be difficult.) Ducke 
(in Bol. 'Téen. Instit. Agron. Norte no. 10 (1946) 13) 
indicates that the seed of Hevea rigidifolia is similar in 
shape and size to that of typical HY. pauciflora. Uf this 
unique seed actually belongs to Hevea rigidifolia, it 
might suggest some relationship with HZ. gwianensis var. 
lutea or H. nitida which have similar angular seeds. We 
cannot draw any definite conclusions, however, on the 
basis of the few known seeds of Hevea rigidifolia. 
In floral characters, however, there is less to point to 
a close affinity between FTevea rigidifolia and H. pauci- 
flora var. coriacea, This is especially true when the dif- 
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