204 NOTES OF ALGÆ, 
The following table indicates the number of British species 
in each genus, those found at Aberdeen, those at 1000 feet, 
and those at lower than 2000 feet, &c., &c. 
* į ^ i ` i E No. of 
No T LEE eia amie xa d nee No T node TT 
Closterium 14 14 9 4 3 
smarium 10 8 9 4 3 
Cylindrocystis 1 1 1 1 i 
Desmidium 2 2 0 0 0 
Didymoprium 2 2 1 0 0 
Euastrum 10 10 5 2 3 
Gleoprium 2 2 0 0 9 
Holocystis 1 1 0 0 0 
Micrasterias 2 2 0 0 1 
Pediastrum | , 4 0 1 0 
Scenedesmus 5 5 1 0 0 
Staurastrum 16 11 7 2 2 
Tetmemorus 2 2 2 2 2 
Xanthidium 4 4 2 0 B 
78 68 Sp 41-3 15 
The large proportion of the British species occurring at 
Aberdeen is worthy of remark; especially as most of them. 
reach also the southern extremity of our island. This may 
be owing to the element in which they live, being little liable 
to rapid changes of temperature: even were it the converse 
probably their low vitality (if the expression may be allowed) | 
might render them less liable to be affected by such changes. 
The proportion occurring at altitudes above 1000 feet, 
