ON SCOTTISH DESMIDIE/E 107 



to be confined to the Atlantic slope are Enastruin divari- 

 catuui, Lund., Staurastnun bidentatum, Wittr., St. setigerum, 

 Cleve, and St. bifiduin, Ehr. ; but a little further investigation 

 may find these over the watershed, as it has found others. 

 It must not be forgotten, however, that the western slope 

 has not been searched with anything like the care bestowed 

 on the eastern. Indeed, it has only been tapped at a few 

 widely separated points : by myself in Sutherland, at Loch 

 Inver ; in Ross, at Poolewe, by Rev. D. Campbell ; in Inver- 

 ness, at Balmacarra, by Mr. Wills ; and by myself in different 

 localities in Skye ; in Argyll, in Glen Coe, and about Oban, 

 by Mr. Wm. Archer ; in Mull, by Dr. Buchanan White and 

 Mr. G. Ross ; between Lochs Lomond and Long, by Dr. 

 Watson ; near the Kyles of Bute, by Mr. Wm. Anderson ; in 

 Bute and Arran, by Messrs. J. and J. P. Bisset ; near 

 Greenock, by Mr. T. Fisher ; and near New Galloway, in 

 Kirkcudbright, by Mr. M'Andrew. I have seen and 

 examined gatherings from all these localities, except those 

 made by Mr. Wills and Mr. M'Andrew. Mr. Wills 

 examined his gatherings himself, and gave the results to 

 Mr. W. Barvvell Turner, Leeds, who kindly sent them to me. 

 Mr. M'Andrew's gatherings were sent to Mr. Wm. West, 

 Bradford, who very courteously placed the results, as well as 

 those of numerous gatherings of his own, from various parts 

 of the country, at my disposal. In " Eng. Fl." vol. v. pt. 

 i., Captain Carmichael records five species from Appin, in 

 the north of Argyll, and in Ralf's " Brit. Desmid." Rev. D. 

 Landsborough records four species from Ayrshire ; but in 

 both cases the species recorded are quite common all over 

 the country. 



These few collections, though good in themselves, and 

 exceedingly useful, are quite insufficient as a basis on which 

 to found any reliable generalisations as to the frequency of 

 the occurrence of species on the Atlantic side of the water- 

 shed as compared with the Germanic, or vice versa. A few 

 rather notable species, which hitherto have proved western 

 in other portions of our islands, have not as yet been 

 detected in Scotland. These are Micrasterias apiculata, 

 Ehr., and M. bracJiyptera, Lund., from Westmoreland ; M. 

 furcata, Ag., Docidium nodosum, Bailey, Staurastrnni OpJiiura, 



