356 Proceedings of the Royal Physical Society. 
prolonged experiments successful (as a rule) results followed. 
Thus, with Limnanthemum nympheoides healthy germination 
occurred after a drying period of thirty months, with Call- 
triche aquatica after twenty-four months, with Myriophyllum 
spicatum and Potamogeton crispus after eighteen months, and 
with Myriophyllum alterniflorum after twelve months. On 
the other hand, the seeds of Nuphar lutewm and Nymphea 
alba lose their vitality after two months’ drying, and prob- 
ably a month’s drying would prove destructive to them. 
Now, if a pond in which flourished Ranunculus aquatilis, 
Nuphar luteum, Nymphea alba, Myriophyllum spicatum, 
Callitriche aquatica, and Zannichellia palustris was dried up 
for some months during the summer, and was refilled by the 
autumnal rains, the result would be the disappearance from its 
waters of the two water-lilies, Nuphar lutewm and Nymphea 
alba, whilst all the other plants above-named would soon be 
thriving again. This was in part illustrated in a pond near 
Kingston-on-Thames, where Ranunculus aquatilis and Myrio- 
phyllum alterniflorum thrived. The pond was dried up for 
some months during the drought of the summer of 1893; 
but in the following year the two aquatic plants reappeared. 
The operation of this principle during the course of ages 
would tend to the exclusion of these two water-lilies from 
pools, ponds, and streams liable to the effects of a period of 
drought. These plants in the lapse of time would, as a rule, 
only be found in rivers, lakes, and ponds fed by rivers or 
perennial springs. This is, in fact, the case. On the other 
hand, Myriophyllum, Callitriche, Zannichellia, ete., would 
frequent not only the waters where Nuphar and Nymphea 
thrived, but also ditches, pools, and shallow ponds liable to 
disappear for a time at each period of dessication, and where 
the water-lilies do not occur. This also is a fact of observa- 
tion. In assigning or limiting a station to particular plants, 
Nature avails herself of the endless variety of their capacities 
—capacities not always very apparent, and often seemingly 
trivial in their character. 
1 For some time I have been endeavouring to approach the problem con- 
nected with the ‘‘station” of plants by various roads, following different 
lines of research for different sets of plants. 
