Joannesia than with either Hevea or Micrandra. The 
structure of the stigmas, on the other hand, is definitely 
micrandroid. 
Dr. Grady L. Webster, Research Fellow in Biology at 
Harvard University, has made a study of the pollen 
grains of Vaupesia and of related genera. His observa- 
tions follow: 
‘The pollen-grains of Vaupesia cataractarum are char- 
acterized by a ‘Croton-pattern’ of ornamentation, as de- 
fined by Erdtman*. When expanded in lactic acid, they 
are spherical, about 72-77 in diameter, and apparently 
non-aperturate. ‘The ornamentation is due to a dense 
exinous layer of knob-like processes arranged, as illus- 
trated by Erdtman for Manihot and Jatropha (op. cit., 
170), in rings of five or six around a dim, circular area. 
The knobs in Vaupesia are about 4u long and roundish 
or 8—5-angled in cross-section. 
“Of the genera in the Hevea-complex, Joannesia 
shows the greatest similarity to Vaupesia in pollen mor- 
phology. The grains of Joannesia princeps are about the 
same size and have a very similar pattern of exinous 
knobs. In fact, one could not, on the basis of pollen 
morphology alone, distinguish the two genera. Micran- 
dra and Hevea, on the other hand, have colporate grains 
and, palynologically, at least, stand further away.”’ 
Are we not justified in believing that Vaupesia rep- 
resents, perhaps, a concept linking more closely the 
Micrandra-Joannesia-Hevea complex? And, likewise, 
may we not interpret Vaupesia as possibly a vestige of 
an ancient prototype of what we now see differentiated 
into Micrandra, Joannesia and Hevea? 
Speciation in both Hevea and Micrandra has occurred 
to a much greater extent in the basin of the upper Rio 
* Erdtman, G.: Pollen Morphology and Plant Taxonomy (1952) 
173. 
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