300 Proceedings of the Royal Physical Society. 
germinated. Fish, no doubt, similarly prepare these fruits 
for germination. Darwin, in his “Origin of Species,” and 
other authors notice the occurrence of these fruits in the 
stomachs of fresh-water fish. They are voided by animals 
bared of their soft coats. My efforts in imitation of the 
process, by baring the “stones” with a knife, failed to induce 
early germination, 
It is of importance to determine to what extent these 
fruits will withstand drying. Those of Potamogeton natans 
germinated freely after drying for four months, but all rotted 
after being dried for thirty months. Those of P. densus 
germinated after drying for eleven weeks, but all rotted after 
drying for seventeen and thirty months. On the other hand, 
the fruits of P. crispus germinated in numbers after drying 
for eighteen months. These facts are sufficient to justify 
the conclusion that Potamogeton fruits retain their powers 
of germination after drying for several months. 
Having noticed that the fruits of Potamoyeton natans 
germinated in water more readily in darkness than in 
diffused light, made a special experiment with the object 
of testing this observation. A large number of the fruits 
were divided into four sets, and placed in four vessels of 
water, two being in darkness and the other two in diffused 
light. The seeds of Nuphar luteum were experimented on 
at the same time in these vessels, and the method of the 
experiment has been already described when treating of that 
plant. The results obtained for Potamogeton natans from 
December to June, when the experiment began and ended, 
were these:—In the greenhouse, 35 fruits germinated in 
bright diffused light and 61 in darkness. In the room, 
226 germinated in diffused light and 217 in darkness; but 
the advantage at first was much on the side of the fruits 
in darkness, of which up to the end of March 150 had 
germinated, against 66 in diffused light. It appears, then, 
that neither light nor darkness is essential to germination, 
although darkness favours it most. The contrary inference, 
as regards the effect of darkness, was drawn for the seeds 
of Nuphar luteum, which were in the same vessels, the 
1 These data were given in Science Gossip for September 1894. 
