80 BRITISH DESMlDIACE^l. 



mere (Bissett), Elter Water!, Grisedale Tarn!, and 

 Stickle Tarn (abundant !), Westmoreland. Cronkley 

 Fell and Lund's Fell, 1S T . Yorks ! Chobham and 

 Thursley Commons, Surrey ! Dartmoor, Devonshire ! 



WALES. Capel Curig ! (Cooke Wills), Snowdon !, 

 bog on Glyder Fach (at 2,200 ft.) !, Carnarvonshire. 

 Dolgelly, Merioneth ! 



SCOTLAND.- -Ross, Inverness !, Aberdeen, Kincar- 

 dine, Forfar, Perth, Argyll and Arraii (Roy fy Bissett). 

 Scourie, Sutherland ! 



IRELAND. Kylemore, G-alway ! Near Carrickmore, 

 Tyrone (Dixon). Dublin and Wicklo^v (Archer). 



Geogr. Distribution. France. Germany. Norway. 

 Faeroes. India. 



This variety is much more frequently met with than typical 

 If. oscitansj and it exhibits considerable variation. Many 

 intermediate forms between the two occur,, and this has 

 resulted in the following names : 



M. mucronata forma intermedia Nordst ("Norges Desm/ 

 1873, p. 6). 



M. oscitans var. mucronata forma intermedia Boldt (1888). 



M. oscitans var. intermedia Turn. (1893). 



As so many of these intermediate forms exist, constituting 

 a complete series connecting M. oscitans with its var. 

 mucronata, there is no justification for giving them varietal 

 names. Both Cooke ancl Wille have figured a number of these 

 intermediate forms. 



M. oscitans var. mucronata is largely an upland species and 

 sometimes occurs in quantity in mountain bogs, generally 

 amongst the leaves of Sphagnum cuspidatum var. plumosum, 

 and very often mixed with Micrasterias Jenneri, Cosmarium 

 Cucurbita, Euastrum insigne, and other Desmids. 



2. Micrasterias pinnatifida (Kiitz.) Half's. 

 (PI. XLI, figs. 7-11, 13.) 



Euastrum pinnatifidum Kiitz. Pliyc. germ. 1845, p. 134. 



E. bifidum Focke, Phys. Stud. 1847, p. 45, t. 1, f. 12, t. 2, f. 22. 



Micrasterias pinnatifida (Kiitz.) Ealfs, Brit. Desm. 1848, p. 77, t. 10, f. 3 ; 

 Kiitz. Spec. Alg. 1849, p. 171 ; Wolle, Desm. U.S. 1884, p. 116, t. 37, 

 f. 7, 8 ; Cooke, Brit. Desm. 1886, p. 54, t. 20, f. 3 ; Hauptfl. Zellinembr. 

 u. Hiillgallerte Desm. 1888, p. 92, t. 3, f . 4-6, 7-9. 14, 16-18 ; West, Alg. 



