142 G. T. HARRIS ON THE 



in their Monograph on the British Desmidiaceae (11) except for 

 that portion of the genus Staurastrum whicli remains uncompleted 

 in the monograph. For this remaining portion I have been 

 compelled to use that of Cooke in British Desmids (12) and 

 WoUe, Desmids of the United States (13). 



The whole of the material which forms the basis of this paper 

 was collected and worked out by myself, consequently I am 

 responsible for any errors of determination, etc. 



The capital letters in the first column of the Census List in- 

 dicating the relative frequency or infrequency of the species, 

 etc., apply to the district as a whole, and not to the individual 

 stations from which it was collected. A species may be fairly 

 common in the particular station from which it was collected, 

 although rarely occurring in the entire district. 



In conclusion, I would offer my sincere thanks to the Quekett 

 Microscopical Club for affording me the opportunity of publica- 

 tion in their Journal ; the more so as I am fully aware of the 

 difficulties under which the scientific societies are labouring 

 to carry on the publication of their proceedings. 



Physical Descriptions of the Bogs from which Collections 

 WERE made. 



Woodbury Common. — This is by far the most important 

 collecting ground in the whole district. It is an elevated ridge, 

 running north from the coast near Budleigh Salterton to near 

 Larkbeare, a distance of some eleven miles, with an average 

 breadth of from one and a half to two miles, and a height 

 varying from about 400 to nearly 600 feet above sea level. This 

 ridge is composed almost continuously of the Budleigh Pebble 

 beds resting on underlying New Red Marls, and is an undulating 

 district of common land, covered with furze, heather and bracken. 

 In the southern portion of the common, on the eastern side, 

 are deep gullies whose bottoms contain small rivulets bounded 

 on either side by boggy margins. These bogs are quite different 

 in formation from those in the northern part. There the bogs 

 are due to springs breaking out at the junction of the under- 

 lying New Red Marls with the Pebble beds, and consist of a shal- 

 low depth of water flowing gently down an inclined surface, 



