dd4 Proceedings of the Royal Physical Society. 
from germinating in the season of their growth. In no 
experiment was germination deferred to the second year. 
With regard to Ranunculus aquatiltis, it may be observed 
that all the British varieties of this species, including 
R. hederaceus, were experimented on. The achenes sink at a 
touch. Their germinative capacity is not impaired by many 
months of drying. Many of the fruits germinate in the season 
of their growth, and the rest all do so in the following spring. 
With regard to the influence of light on the germination of 
the sunken fruits, it may be said that darkness prevents or 
retards the process. This was well brought out in an experi- 
ment on Ranunculus hederaceus, where the same thermal 
conditions were secured by placing the two vessels beside 
each other, one being exposed to diffuse light, the other being 
covered over so as to produce darkness. The experiment 
was begun on June 27th; and whilst in the exposed vessel 
all had germinated by July 23rd, in the darkened vessel only 
5 per cent. had germinated up to August 9th, when it was 
exposed to diffuse light, and in five days all but 20 per cent. 
of the fruits had germinated. ‘This behaviour is precisely 
that exhibited by the fruits of Callitriche aquatica under the 
same conditions of experiment. 
Recurring once more to the subject of the postponement of 
germination of aquatic plants, attention should be paid to the 
latter part of the Table, where I have given examples, which 
might have been largely increased in number, of the post- 
ponement of germination in water on the part of land-plants. 
The seeds or fruits of nearly all the plants here named form 
constant constituents of the floating seed-drift of ponds and 
rivers, and that which occurred in my experiments on this 
drift, without a doubt also occurs in the pond and in the 
river! This is not the place to enter into any detail about 
this matter. It will be enough to state that not only did 
the seeds or fruits of these and other land-plants germinate 
in the vessels of water after floating or lying at the bottom 
for two or three years, but they performed the process com- 
pletely, and vigorous seedlings were raised from them. 
1 River drift was dealt with by the author in a paper in vol. 29, Linn. Soc. 
Journ. Bot. For pond drift see also Science Gossip for October 1895. 
