158 BRITISH DESMLDIAOE^]. 



IRELAND.- -Donegal ! Mayo ! G-alway ! Kerry ! 

 Dublin and Wicklow (Archer). Armagh! London- 

 derry ! Plankton of the lakes of Galway and Kerry ! 



Geocjr. Distribution.- -France. Germany. Switzer- 

 land. Austria and Galicia. Italy. Norway. Sweden. 

 Faeroes. Greenland. Spitzbergen. United States. 

 Brazil. Argentina. 



This species is generally distributed throughout the British 

 [glands, occurring commonly at the margins of lakes or of old 

 ponds and pools, and in boggy springs. It is characterized 

 by its reniform semicells, the form of which is in a large 

 measure due to the widely dilated extremity of the sinus. 

 The granulation of the cell-wall is one of the most pronounced 

 features of the species. The marginal granules (approximately 

 30 on each semicell) often stand out like rounded beads, and 

 the granules as a whole are disposed in slightly curved series 

 crossing one another obliquely. In some individuals the 

 granules are more or less evidently disposed in vertical series, 

 but there is often considerable irregularity in the whole 

 granulation. 



C. reniforme has very little in common with (7. margariti- 

 ferum. 



The zygospore was first discovered in Ireland by Archer, 

 who pointed out its smooth and g'lobular character. 



Liitkemuller has recorded Austrian specimens of C. reni- 

 forme with a length of 57-74 /LI and a breadth of 50-62 /u, but 

 British forms do not attain such dimensions. 



Var. compression Kordst. (PI. LXXIX, figs. 3, 4.) 



C. reniforme (Ralfs) Arch. var. compressum Nordst. in Bot. Notis. 1887, 

 p. 159 ; Freshw. Alg. N. Zeal. 1888, p. 46, t. 5, f . 5 ; West, Alg. Engl. 

 Lake Distr. 1892, p. 727 ; Turn. Freshw. Alg. E. India, 1893, p. 73 ; 

 Eacib. Desm. Tapakoomas, 1895, p. 33 ; West & G. S. West, Some 

 Desm. U. S. 1898, p. 307, t. 17, f. 10 ; G. S. West, Alga-fl. Cambs. 1899, 

 p. 217 ; West & G. S. West, Alg. N. Ireland, 1902, p. 38. 



Semicells depressed, with the median part of the 

 apex sometimes slightly truncate; vertical view elliptic- 

 oblong or oblong, narrower than in the typical form. 



Length 46-64 ^ ; breadth 4756 /n ; breadth of 

 isthmus 13-18 /n ; thickness 24-28 /u. 



ENGLAND.- -Hawkshead, Lancashire ! Twenty-foot 

 River, between March and Guyhirne, Cambs ! 



