species, however, the lobes of the disk in the staminate 
flower are similar, being rather elongate, very acuminate 
and conspicuously erect-spreading. The lax and irregu- 
larly spreading long-acuminate tips of the calyx lobes of 
the female flower of Hevea rigidifolia, however, has no 
similarity to any of the forms of H. Benthamiana known 
to me; indeed, the female flower of Hevea rigidifolia, 
which, upon superficial observation would seem to be 
somewhat like that of HY. microphylla, appears to be 
unique in the genus in this interesting characteristic. 
The characters of the ligneous valves of the fruit have 
hitherto not been utilized taxonomically, but it is of great 
interest to note in passing that those of Hevea rigidifolia 
are very like those of most of the known forms of Hi. 
Benthamiana in having an unusually thin endocarp. The 
long and narrow shape of the valves of Hevea rigidifolia 
is very different from that which is commonly seen in 
HI. Benthamana, but it does remind one of the shape of 
the valves of H. Spruceana. Ducke (in Bol. Téen. Instit. 
Agron. Norte no. 10 (1946) 18-14) indicates that a speci- 
men collected by him in 1905 on the Rio Negro at Bar- 
cellos and distributed by Huber as ‘‘Hevea rigidifolia”’ 
is a form of HI. Benthamiana var. subglabrifolia Ducke 
with perfectly glabrous leaflets. (See also Ducke in Arch. 
Instit. Biol. Veg. 2, no. 2 (1985) 235 and in Arquiv. Serv. 
Florest. Rio de Janeiro 2, no. 1 (1948) 86.) 
Recently in Belém, I had occasion to study a remarka- 
ble collection of Hevea Benthamiana from the Rio Ne- 
gro which Ducke has determined as representing a per- 
fectly glabrous form of var. subglabrifolia.” 1 believe 
that further study will possibly indicate that this collec- 
tion represents a distinct variety. The reclinate leaflets 
'S Brazil: Amazonas, Rio Negro infer., loco Acajutuba. ‘‘Igapé 
secus rivulum ad marginem campinae. Arbor 18-20 m.; latex flavi- 
dus, parum copiosus.’’ March 22, 1941, Ducke 1963, 
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