COSMARIUM. /'O 



WALES. Capel Curig and Llyn-y-cwm-ffynon, Car- 

 narvonshire ! 



SCOTLAND.- -Sutherland !, Ross, Inverness!, Moray, 

 Banff, Aberdeen, Kincardine, Forfar, Perth !, Fife, 

 Stirling, Dumbarton, Argyll, and Arran. Zygospores 

 from Folotry, Perth (Pioij $ Bissett). Orkneys and 

 Shetlands ! Common in the Outer Hebrides ! 



IRELAND.- -Donegal ! Lough Aunierin, G-ahvny (with 

 zygospores) ! Xear Lough Brin, Lower Lake of 

 Killarney, and Lough Guitane (with zygospores), 

 Kerry ! Dublin and YTicklow (Archer]. Armagh ! 

 Slieve Donard, Down ! 



Geoyr. Distribution. France. Germany. Austria. 

 Silesia in Austria. Xorway. Sweden. Denmark. 

 Bornholm. Poland. Faeroes. Greenland. Japan. 

 India. Ceylon. United States. Patagonia. Australia. 



J O 



C. pygmssum is a species which is almost confined to 

 Splicuj)tiiiii-\)ogs and to small peaty pools with an abundance 

 of submerged Sphagnum. In these situations it sometimes 

 occurs in countless millions, and pure collections of it can 

 easily be made. It is a Desmid about which there has been 

 much misunderstanding in the past, possibly owing to its 

 minute size and its variability. Dr. Lutkemiiller has found 



V 



the species abundantly in Austria, and he is in complete 

 agreement with us regarding 1 its synonym v. AVe are likewise 



o O O /// 



indebted to him for drawings of his Austrian specimens, some 

 of which we have reproduced. 



In external form the semicells exhibit much variation, and 

 the same remark applies to the median protuberances and 

 papillae of the vertical view. The most widely distributed 

 form has an oblong-rectangular semicell, in which the upper 

 angles are somewhat obliquely truncate, and the lateral angles 

 thus formed are faintly produced into a minute mucro. This 

 same form in vertical view has a median protuberance and 

 two papillae on each side. AVe have refrained from any 

 attempt to arrange the forms as all possible gradations exi-t 

 between the extremes figured on PL LXXI. 



It is probable that C. silesiacum G-utw. (' Wahr. d. Prioritat/ 

 1890, p. 69; f Flor. Glom. Okolic Lwowa/ 1891, p. 55) should 

 be placed as one of the forms of C.pygmaeum, but an examina- 

 tion of the specimens is necessary to decide the question. 



