346 Proceedings of the Royal Physical Society. 
set side by side so as to ensure the same thermal conditions, 
one being left exposed to diffused light, and the other being 
covered so as to be always in darkness. The experiment 
was prolonged to June 10th, and during this period 54 seeds 
germinated in the exposed vessel in the greenhouse and 21 
in the covered vessel. In the room 186 seeds germinated in 
the exposed vessel and 56 in the covered vessel. The infer- 
ence is that whilst these seeds will germinate in the dark, 
they will germinate in much greater numbers when exposed 
to diffused light. 
In Experiments 1, 6, and 7, the seeds of Nuphar and 
Nymphea germinated freely after being inclosed in frozen 
mud for two weeks without a thaw; the mud was through- 
out as hard as stone. Amongst the methods of promoting 
early germination of Nuphar seeds may be mentioned that 
of immersion in sea-water, as is indicated in Experiment 4. 
With Nymphea alba the contrary is the case. Of seeds that 
had been lying six weeks in sea-water, only 4 per cent. 
germinated and the rest rotted. 
The fruits of Myriophyllum spicatum germinated readily in 
most of my experiments in the year of their growth from 
September on to December. In this respect this plant differs 
from most of the aquatic plants named in the Table. Occa- 
sionally this does not happen, and the process, as indicated 
in Experiment 12, may then be deferred to the second year. 
Free germination occurred in the case of fruits of JZ. spicatum 
that had been kept dry for eighteen months, and of those of 
M. alterniflorwm which had been kept dry for a year. Lying 
sunken in water, both in darkness and in bright diffused 
light, and under the same thermal conditions, the fruits of 
both these species germinated with equal readiness. An 
inclosure in ice for two weeks did not impair the germinating 
capacity. 
The postponement of germination is well illustrated in the 
Table in the case of the seeds of Limnanthemum nympheoides. 
These seeds are well able to withstand prolonged drying, and 
in the course of the experiments some germinated healthily 
in water after drying for thirty months. Inclosure in ice and 
in frozen mud for some weeks favours rather than hinders 
