148 G. T. HARRIS ON THE 



the great abundance of various species of Pleurotaenium and 

 Docidium, clearly indicating a preference for a lowland habitat. 



Micrasterias Americana and vars. This species was only 

 once collected. It occurred with the two varieties given in the 

 Census List in an almost dried-up depression on Woodbury 

 Common, containing scarcely any water beyond the small 

 amount present in the sphagnum growing there. 



Cosmarium ohlongum Benn. After careful examination of 

 several specimens gathered on Woodbury Common, I have come 

 to the conclusion that they are really so near Bennett's descrip- 

 tion of C. ohlongum that they should be so named, as the species 

 is admitted to the British Desmidiaceae. The measurements 

 of the Woodbury Common specimens are too small for C. Hiherni- 

 cum West, and not small enough for C. viride (Corda) Joshua. 

 It would undoubtedly be better to sink Bennett's species to a 

 variety of C. viride to which it obviously belongs. 



C. Corbula Breb. This is a very rare Desmid in Devonshire, 

 and was met with in only one locality, where, however, it occurred 

 in some profusion and with plenty of zygospores. 



Desmidium Swartzii Ag. This Desmid is much more plentiful 

 in East Devon than it is on Dartmoor, at the same time it is 

 by no means common. It would appear to be a species that 

 finds its most favourable habitat in lowland, still ponds, as I 

 have collected it in great quantities in the New Forest district, 



Desmidium cylindricum Grev. In the hot, dry summer of 

 1919 this species occurred in prodigious quantities in the Ex- 

 mouth Reservoir, in such long filaments that in the water the 

 growing mass had the appearance of a species of Spirogyra or 

 Zygnema. 



Literature Cited and Consulted. 



(1) Parfitt, E. : Devon Freshwater Algae. Transactions of 



the Devonshire Association, 1886. 



(2) HiERN, W. P. : Victoria County History, vol. i. 



(3) West, W. and G. S. : A Contribution to the Freshwater 



Algae of the South of England. Journal of the R.M.S., 

 1897. 



(4) Joshua, W. : Notes on British Desmidiae. Journal of 



Botany, xxi. (1883) p. 290. 



