DESMID FLORA OF A TRIASSIC DISTRICT. 147 



floating in long streamers in the swift water of tlie river. These 

 fine rootlets were crowded with innumerable individuals of the 

 above species attached by one apex of the cell. The velocity 

 of the river at this spot, added to the turbulent tossing to and 

 fro of the rootlets in the water, enabled one to form an estimate 

 of the adhesive properties of the mucilage excreted by the 

 Desmid. 



Special Notes on Some Species. 



Spirotaenia fusiformis, W. and G. S. West. This rare species, 

 only recorded in West's British Desmids from Cowgill Moss, 

 Yorks., occurred in the southern portion of Woodbury Common 

 in a small well-aerated bog. 



Mesotaenium De Greyi var. hreve W. and G. S. West. Hitherto 

 only recorded from the Tore Mountains. 



Mesotaenium purpureum W. and G. S. West. Only recorded 

 from Cote Moor, Yorks. The Woodbury Common specimens 

 are smaller than West's measurements. 



Cylindrocystis Brehissonii Menegh. This common and wide- 

 spread Desmid occurred in prodigious quantities in the intake 

 beds of the Exmouth Reservoir on Woodbury Common. Large 

 masses of mucilage floating in the water consisted of practically 

 pure gatherings of this Desmid. 



Netrium intenwptum W. and G. S. West. So many specimens 

 of this species were collected on Woodbury Common with con- 

 tinuous, undivided chloroplasts that it may be doubted if the 

 interrupted chloroplast is of any specific value. 



Closterium praelongum Breb. Apparently a very rare Desmid 

 in Devonshire. The Exeter Canal at Countess Weir is the only 

 station from which I have collected it. 



Closterium Malinverianum De Not. A rare Desmid in Devon- 

 shire, and almost entirely confined to sluggish streams, such as 

 the canal at Countess Weir. 



Docidium haculum Breb. The late Professor G. S. West, 

 in a letter to me, remarked on the absence of this Desmid and 

 Pleurotaenium truncatum (Breb.) Nag. from the Dartmoor census 

 list. {Journal Q.M.C., vol. xiii, April 1917). In the East Devon 

 district they occur, but with no great frequency. In the New 

 Forest during a recent coUecting trip, I was at once struck with 



