34 West & West. — Observations on the Conjugatae. 
and in ordinary seasons in all probability they never do 
conjugate. How, then, are they preserved throughout the 
winter? It must be by means of the survival of some of the 
plants (without the formation of spores) through the prolonged 
freezing they have to undergo, which is followed by their active 
division in the spring. We can also mention instances of this 
in the Desmidieae. There is a small peaty ditch in Eldwick, 
on the edge of Rombald’s Moor, W. Yorks., in which count- 
less numbers of Micrasterias denticulata have occurred in 
a perfectly pure state for very many years. We have 
examined this ditch carefully at all times of the year, and 
always find some specimens of this Desmid, even when it is 
frozen ; but never once have we come across a single zygo- 
spore from this locality, although constant search for them 
has been made. Here, then, the perpetuation of the species 
must be dependent upon the survival of some of the ordinary 
vegetative plants through the winter ; and we may mention 
that the locality is a bleak one, its altitude being near 
1,000 feet, and the water is generally frozen for some weeks 
during the winter. 
It is also worthy of note that in all the contributions to the 
Algal Flora of the Arctic regions yet published, the occur- 
rence of the zygospores of Desmids has seldom been mentioned, 
though many species are recorded from places noted for their 
intense cold in winter, for instance, Greenland, Spitzbergen, 
Nova Zembla, and northern Siberia. We have a species of 
Oscillatoria from a valley in the Davos Platz district in 
Switzerland, collected by Mr. A. Howard in August, 1897, 
from a stream at 8,000 ft. elevation with the temperature of 
the water at 5°C. This is the summer condition, and the 
winter one may be easily imagined ; we must therefore reject 
Mr. Ewart’s statement that ‘ owing to their slight powers of 
resistance to cold, the temperatures to which they can be 
exposed without being permanently injured are necessarily 
relatively high.’ Stationary masses of water, such as pools 
and small lakes, even at this altitude, attain during summer 
a comparatively warmer temperature than the streams ; a lake 
