West & West. — Observations on the Conjugatae. 33 
been noticed in an incomplete form in Zygnema pachydermum , 
var. conferv aides 1 . 
With regard to the effect of temperature on the Conjugatae, 
a paper by Alfred J. Ewart, entitled ‘ On Assimilatory Inhibi- 
tion in Plants,’ has recently appeared 2 , in which the author 
states (p. 395) that ‘ freshwater Algae . . . are not very resistant 
to cold, all those examined being killed by being frozen. 
This statement we cannot agree with, as we have found them 
to be very resistant to cold, and as a large number of the 
plants belonging to the Alpine Algal flora are Conjugates we 
illustrate the matter by a few examples. 
We have melted out of the ice from Mitcham Common, 
Surrey, excellent examples of Spirogyra catcieniformis in 
a state of conjugation, the vitality of which was in no way 
impaired. From Frizinghall, W. Yorks., we have also melted 
out of the ice hundreds of specimens of Closterium Leibleinii , 
which subsequently remained in a perfectly healthy and 
normally active condition (moving to that side of a vessel 
exposed to most light, just as we find all other species of 
Desmids to act), and in each of these cases the specimens 
examined had been frozen for over fourteen days. These 
facts alone disprove the generality of Mr. Ewart’s statement ; 
but let us now consider some still more convincing ones. 
Many of the upland tarns of Yorkshire, the Lake District, 
the Scotch Highlands, and other places, are situated at 
altitudes of over 2,000 feet, some of them being much higher, 
and the water in them is of a relatively low temperature even 
in summer. For many months in the winter these tarns are 
frozen, and the small ones often buried in deep snow drifts, 
although by the middle of summer they are fairly crowded 
with filamentous Algae, of which the most abundant forms 
are small species of Mougeotia. We have never yet seen these 
species of Mougeotia in conjugation from these altitudes 3 , 
1 Cf. West, l.c., PI. XIV, Fig. 5. 
2 Joum. Linn. Soc. Bot., Vol. xxxi, 1896, No. 217. 
3 We have examined sterile species of this genus, obtained at 3,000 feet in the 
Scotch Highlands and 6,500 feet in Switzerland. 
D 
