Germination of the Sceds of Aquatic Plants. 349 
—as in Experiment 27—none of the seeds germinated in the 
first year, and nearly all in the second year. In Experiments 
28 and 29, the seeds were seventeen days in ice during the 
first winter ; and in the one case about half, and in the other 
all of the seeds germinated during the first year. These 
seeds withstand a prolonged inclosure in ice better than the 
seeds and fruits of almost every other aquatic plant experi- 
mented on. The effect of drying for some months, and of 
prolonged flotation in sea-water, is to put off the germinating 
process to the second year. 
Coming to the Potamogetons, it is not possible here to 
enter into any details relating to the somewhat complicated 
history of their fruits in our ponds and rivers. In such 
a case it would be necessary to distinguish those with buoy- 
ant fruits from those without, and to look into the habits of 
each species in so far as it bears on the history of the fruit. 
Here I will merely deal generally with the postponement of 
germination, and with some of the influences that favour or 
impede the process. That the delay of germination for years 
is a characteristic feature with these plants is strikingly 
illustrated in the Table. Whilst it is there demonstrated 
that these fruits can defer the process, when in wet mud, to 
the fifth year, and in water to the fourth year, an analysis of 
the results leads to the conclusion that in water the delay 
will be protracted on to the fifth, and even to the sixth year. 
Here, however, as with the Sparganiums, the aquatic bird 
sometimes intervenes as an agent, and by swallowing the 
fruits and voiding them uninjured, it prepares them for early 
germination. The fruits of Potamogetons were found by the 
author in the stomachs of three out of thirteen wild ducks— 
the total number found being forty-one. Of these fruits, 
twelve were placed at once in wet mud, and in four months 
time all had germinated. A large number of the fruits of 
Potamogeton natans were mixed with the food of a domestic 
duck. They were found in the droppings in quantities 
unharmed, and of these 60 per cent. germinated in the 
following spring. Of those left in the vessel from which the 
duck had been fed, only 1 per cent. germinated in the next 
spring, and another year passed before any number of them 
