Germination of the Seeds of Aquatic Plants. Bd8 
The effect of light on the germination of these Jris seeds 
was tested in the same vessels of water, and contempor- 
aneously with the seeds of Nuwphar lutewm and the fruits of 
Potamogeton natans, as already described. Thirty seeds were 
placed in December in each of the four vessels, one in bright 
diffused light and one in darkness in the greenhouse, and 
one in diffused light and one in darkness in the room. Up 
to June, fourteen seeds had germinated in the darkened 
vessel in the greenhouse, and none in any of the other 
vessels. 
Reference may here be made to one or two other aquatic 
plants which are not referred to in the Table. 
The fruits of Zannichellia palustris germinate in fair pro- 
portion in the year of their growth. They also germinate 
freely in water after four and a half months’ drying. 
The fruits of Callitriche aquatica, which, it should be 
remarked, do not float, germinated well when placed in 
water after two years’ drying. They failed to germinate, and 
rotted when the drying period was extended to three and a 
half years. The opposite conditions of ight and darkness 
display a marked difference in their effects on the germina- 
tion in water of these fruits under the same thermal con- 
ditions. If the experiment is begun in the middle of the 
summer, most of the fruits exposed to diffused ight germinate 
in a few weeks, whilst none or scarcely any of the fruits in 
the dark will have germinated by the autumn; but by then 
exposing those in the darkened vessel to diffuse light, brisk 
germination of most of the fruits begins in a few days. If, 
on the other hand, the fruits are kept in the dark through 
the winter, few or none of them will germinate even in the 
spring until exposed to the light. These fruits, in my experi- 
ments, readily germinated in the year of their growth. I 
have found them at the end of summer and in the autumn 
germinating in numbers at the bottom of ponds where light 
could reach them. It, however, came out in the experiments 
that a slight covering of fluffy mud, assisted by the shade of 
the floating foliage, will in ponds prevent the sunken fruits 
1 The mode of the experiment is described in the remarks on Nuphar 
luteum. 
