CYLTNDROCYSTIS. 59 



EN<;r,AND. Widely distributed all over the country. 

 Zygospores from Westmoreland, Yorkshire, and Surrey ! 



WALKS. Common and often with zygospores! I'p 

 to 2,200 ft. on Glycler Facli ! 



SCOTLAND. -- General and frequently conjugated! 

 (If ni/ 4'- liiwlt). Up to o,.5()0 ft. on Lochnagar! 

 Outer Hebrides! Orkneys! Shetlands ! 



1 1; i : LAX D. General and often abundant! 



Hi'utj. Distribution. Generally distributed in Europe. 

 Faeroes. Iceland. Greenland. Spitzbergen. Nova 

 Zembla. Franz-Joseph Land. India. Siam. Java. 

 Australia. New Zealand. E.Africa. North and South 

 America. West Indies. Azores. 



Pure gatherings of this species are not uncommon, especially 

 in peaty districts, often at elevations of over 2,000 ft. It 

 sometimes occurs on vertical faces of peat on mountains 

 subject to frequent mists and rain. It is one of the commonest 

 of British Desmids, and occurs in all kinds of damp and wet 

 situations. 



Var. minor West & G. S. West. (PI. V, fig. 11.) 



C. Brebissonii var. minor West & G. S. West, Alg. N. Ireland, 1902, p. 20, 

 t. 2, f. 7. 



Cells narrower and shorter than in the typical form. 



Length 27-41 ^u ; breadth 12'5-13/t; length of 

 zygosp. 33^u, breadth 30^. 



ENGLAND. Mickle Fell and Strensall Common, N. 

 Yorkshire (with zygospores) ! 



SCOTLAND. Pure gathering from Sligachan in Skye, 

 Inverness ! 



IRELAND. Lough Fea, Londonderry (with zygos- 

 pores) ! 



2. Cylindrocystis crassa De Bary. 

 (PI. IV, figs. 33-38.) 



Cylindrocystis crassa De Bary, Conj. 1858, p. 37. 74, t, 7, f. C 1-12 ; 

 Nordst. in Wittr. & Nordst, Alg. Exsic. 1879, no. 269; Cooke, Brit, 

 Desm. 1886, p. 40, t. 18, f. 2 ; West, Alg. W. Ireland, 1892, p. 131 ; 

 West & G. S. West, Alga-fl. Yorks. 1900, p. 43 ; Alg. N. Ireland, 1902, 

 p. 20 ; Desm. Singapore, 1897, p. 156 ; Alg. S. England, 1897, p. 478. 



Peniwn crassa Wolle, Desm. U.S. 1884, p. 37, t. 5, f. 3. 



