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PHYSIOLOGICAL STIMULI AND ITS SIGNIFICANCE 233 
had also germinated but their number was smaller than that in a 20 % 
solution of cane-sugar ; 
in a 10 % solution, I saw but a few plurinuclear pollengrains, which 
had germinated; here also they had formed distended tubes; 
ina5 % solution some plurinuclear pollengrains also had germinated 
but the tubes had attained but a very small length; usually the intine 
protruded but little through the point of rupture of the exine. 
Moreover a positive result was often obtained, when the pollen was 
put into a hanging drop containing a small crystall of cane-sugar. 
It results not only from these germination experiments, that abnor- 
mal, plurinuclear, pollengrains are able to sprout as well as normal fer- 
tile ones, but also that they can be more easily induced to sprout in a 
solution of cane-sugar than the latter. 
It has been mentioned already, that multinuclear pollengrains were 
seen to have frequently sprouted when still inside of the unopened 
anthers of Yellow Hammer abn. N. and abn. W. The fact, that ripe, plu- 
rinuclear, pollengrains from opened anthers could be induced to sprout in 
canesugar-solution made me hope, that such pollengrains might be able 
to fertilise eggcells. 
As to the germination-power of the large globular pollengrains, fil- 
led with starch grains, but little could be determined. It resulted from 
the presence of free floating numerous starchgrains in the sugar solu- 
tion that they had frequently bursted, in the way they did in water. 
Whether they ever sprouted, and, ifso, whether they formed a pollen- 
tube of the type of the normal fertile pollengrains or of that of the ab- 
normal, plurinuclear, ones could not be determined. From the fact that 
pollentubes of normal aspect differed greatly in their dimensions one 
might perhaps conclude to the former of these two alternatives, but it 
may not be lost out of sight that such differences also occur when nor- 
mal fertile pollengrains only, germinate. On the other hand, the fact 
that sometimes pollengrains — the circumference of the exine of which 
was equal to that of the plurinuclear pollengrains — were observed 
with a bladderlike tube full of starch-grains, one might feel inclined to 
prefer the latter alternative. 
This point will have to be investigated a new. 
