COSMAE1UM. 201 



Hebrides ! Orkneys ! Shetlands ! Zygospores from 



south of Birsemore, Aberdeen (li<>>/ $' Bissett),a,nd also 



from Harris, Outer Hebrides ! Bare in the plankton ! 



IKELAXD. General in Donegal !, ]\lavo (with zvo-o- 



O K i ' 



spores) !, Gahvay !, and Kerry ! Dublin andWicklow 

 (Ai-cher). Down ! Antrim ! Lough Xeagh ! Some- 

 what rare in the plankton ! 



(jreofjr. Distribution.- -France. Belgium. Germany. 

 Switzerland. Austria. Poland, Hungary. Italv. 



O , / 



Faeroes. Norway. Sweden. Bornholm. Denmark. 

 Finland. Russia. Bosnia. Iceland. Greenland. 

 Siberia. Java (form). Xew Zealand. Azores. United 

 States. Mexico. Brazil. 



Xo species of the genus Cosmarium has been so misinter- 

 preted, or has given rise to greater confusion,, than C. iiiar- 

 garitiferum. This has been due in large part to the lack of 

 discrimination of the earlier workers at the Desmidiaceae, who 

 regarded almost any granulated Cosmarium under a certain 

 size as C. margaritiferum. Even Ralfs included three species 

 (riz. : C. reniforme, G. margaritiferum, and C. Tiirnerii) in his 

 figures of it, and the typical form has since received at least 

 one new name. The zygospore of true C. margaritiferum, 

 which was well described bv both Ralfs and Archer, is 



V 



globose, and its walls are furnished with scattered thickenings 

 which have been likened to " bull's-eyes." As the species 

 was understood by some of the earlier observers it was un- 

 doubtedly common, and it possessed this characteristic zygo- 

 spore. 



Ralfs' figures of this Desmid are not good. He did not 

 sufficiently indicate the flattened apices of the semicells, nor 

 did he figure the intergranular punctulations and the minute 

 scrobiculations of the central area of the semicells. His figure 

 2J, and possibly 21 and 2c, are the only ones which approxi- 

 mately represent the species. 



In 1894 Schmidle described under the name of " C. Matin- 

 vernianum var. Badense," a Cosmarium which is very abun- 

 dant in the bogs of the British Islands, and in other parts of 

 Europe. It occurs principally amongst Sphagnum, and does 

 not disagree with the published but incomplete descriptions 

 of C. margaritiferum. Moreover, it is of the same size, and 

 its zygospore, which we have found repeatedly, agrees exactly 

 with that described and figured for C. margaritiferum. It is 



