species. Lam unable, however, to see Hevea microphylla 
as one of the older concepts. On the contrary, the curi- 
ous marginal distribution of Hevea microphylla could be 
interpreted to indicate that the species is a relatively new 
one, although what we believe to be the older concepts 
of Hevea are found abundantly represented in the same 
area. Ecologically, it occupies localities similar to those 
chosen by Hevea Benthamiana and H. Spruceana, 
neither of which has seemed to me to represent the most 
ancient species of Hevea. If it arose recently, we could 
wonder and well ask: ‘‘What were its prototypes?” To 
find an answer by studying the comparative morphology 
of the plant may not, at the present state of our knowl- 
edge, be an easy task, nor a productive one. 
It is possible that further exploration will yield an as 
yet unknown species of Hevea which will provide some 
phylogenetic linkage between Hevea microphylla and 
some of the better known species. Until some such clew 
is available and, lacking experimental evidence of a ge- 
netic nature, the immediate affinities of Hevea micro- 
phylla must remain a thought-provoking mystery. 
ECOLOGICAL RELATIONS OF HEVEA MICROPHYLLA 
Usually one finds Hevea microphylla growing on the 
sandy rims of islands or along creeks near the main river 
and, therefore, subject to deep and long inundation. In 
both habitats, the soil is light, almost always of a sandy 
or lateritic nature, and highly acidic. The small bar-like 
islands have a low vegetation which allows the individuals 
of Hevea microphylla, small though they be, to grow in 
numerous, rather congested colonies and often to pro- 
trude well above the competing vegetation. Usually in 
the island sites, no other species of Hevea occupies the 
margin where Hevea microphylla is found. If the island 
be large enough, then Hevea Benthamiana can almost 
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