est species along the deeply flooded banks with low vege- 
tation from the mouth up to San José. It is unusually 
abundant in some places. In one locality (9783) there 
were forty-two trees in one hektar! At another, farther 
upstream near T'apurt, twenty-six. At some points, it 
grows ina very slender band exactly at the water’s edge; 
but, where the bank immediately rises to form high land, 
it stops and is replaced by Hevea guianensis var. lutea 
and HZ. pauciflora, the latter more frequently near sand 
than the former. At one place, Hevea microphylla was 
growing in great abundance, and twenty-five feet away 
from several large trees there were a number of individ- 
uals of HZ. guianensis var. lutea. The former were all 
in ripening fruit, the latter not yet in flower. There was 
not the slightest indication in any of these individuals 
that crossing had happened. Hevea Benthamiana has not 
been seen along the Icana so far, and it would not sur- 
prise me to find it absent from this river. It may be sig- 
nificant that the many Indians here, although producing 
chicle and sorva, never have produced rubber. ”’ 
An incidental note entered during my work near Sao 
Felipe describes the separation of Hevea microphylla and 
HT. Benthamiana: ‘‘Around Sao Felipe, ‘seringueira 
barriguda’ or ‘seringueira torada’ (Hevea microphylla) 
is extraordinarily common and abundant. The right bank 
of the river from well above the mouth of the Igana 
well as the lower 50 kilometers of the Icana itself—is 
populated with Hevea microphylla to the exclusion of all 
other species in the floodlands. On the opposite bank, 
this species is found in the creeks, but Hevea guianensis 
var. dutea controls the highest banks, whilst HY. Ben- 
thamiana takes over the floodbanks. Hevea microphylla 
and H. Benthamianaare seen together below Sao Felipe, 
but only the former species occurs in the extensive 
‘lakes’ which open out below Sfio Felipe—and there 
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