which is conspicuous not in the flowers but also at the base of 
the fruit. A torus is present, of course, in the pistillate flowers 
of all species but, except for Hevea pauciflora, it 1s so incon- 
spicuous as to be for all practical purposes of taxonomic use 
essentially non-existent. In H. pauciflora, it is sufficiently pro- 
nounced as to be easily visible, but it in no way approaches the 
size and conspicuousness of that of H. microphylla, nor is it 
obvious at the base of the ripened fruit. 
The fruit is unique in being pyramidal, triangular in cross 
section, conspicuously keeled and with a long-acute apex. The 
carpel walls are thin and leathery, made up of a thick-papery 
pericarp and an excessively thin, coriaceous endocarp. In all 
other species, the capsule is subglobose, ovoid or ellipsoid, 
trigastic or round in cross section, and emarginate, with a 
rounded or slightly mucronate tip. The carpel walls are thick 
and ligneous, made up of a more or less fleshy pericarp and a 
heavy, thick, woody endocarp. 
This unique structure of the capsule of Hevea microphylla is 
strongly reflected in the method of seed dissemination. In H. 
microphylla, the capsule dehisces slowly, not explosively, and 
the valves open gradually, twisting as they dry out, and adhere 
to the receptacle long after dehiscence. The seeds gently drop 
directly from the capsule and are not propelled violently a great 
distance fron the tree. In all other species, the capsule opens 
explosively, usually sending the seeds in several directions far 
beyond the area beneath the crown of the tree. The heavy, 
ligneous valves contort only slightly, if at all, and fall to the 
ground at the moment the capsule bursts open and frees the 
seeds. Only in Hevea Spruceana are the heavily ligneous val- 
ves persistent and, although the capsule does open explo- 
sively, the seeds are not propelled so far as in other species, 
primarily because of their greater size and weight. 
IV. INFRAGENERIC CLASSIFICATION 
Hevea Aublet, Hist. Pl. Guian. Frang. 2 (1775) 871. 
Subgenus Hevea 
Typus: Hevea guianensis Aublet 
Flos pistillatus toro valde inconspicuo, capsula matura haud 
2a) 
