74 BRITISH DESMIDIACILE. 



1868, p. 167 ; Kirchn. Alg. Schles. 1878, p. 153 : Cooke, Brit. Desm. 



1886, p. 92 ; De Toni, Syll. Alg. 1889, p. 1046. 

 Ursinella pygw&a Kimtze, B/evis. gen. plant. 1891, p. 925. 

 U. Schliephackiana Kuntze, I.e. p. 925. 

 Cosmariiun minutissimum Heimerl, Desm. alp. 1891, p. 600, t. 5, f. 1-i 



[not C. minutissimum Arch., 1877] ; consult Liitkem. Desm. Mills- 



tattersees, 1900, p. 11. 

 C. Heimerlii West & G. S. West, Eec. publ. Desm. 1895, p. 5 (sep.) ; Alg. 



S. England, 1897, p. 486. 

 C. Heimerlii var. tumidum West & G. S. West, Notes Alg. I, 1898, p. 4 



(sep.) ; Alga-fl. Yorks. 1900, p. 91. 

 C. pygmxum Arch. var. Schliephackianum (Gran.) West & G. S. West, 



Some Desm. U. S. 1898, p. 302 ; Alg. N. Ireland, 1902, p. 34. 



Cells minute, as long as broad, or slightly broader 

 than long, deeply constricted, sinus narrow and linear; 

 semicells somewhat variable in form, commonly trans- 

 versely oblong-rectangular, more rarely oblong- 

 hexagonal, basal angles obtuse, upper angles com- 

 monly very slightly obliquely truncate, lateral angles 

 often minutely mucronate (almost produced into a 

 papilla), apex widely truncate, straight or convex, 

 rarely very slightly retuse, with a scarcely conspicuous 

 protuberance in the middle of each semicell, and a 

 minute papilla (sometimes absent) within each lateral 

 angle. Side view of semicell subcircular, with or with- 

 out a prominence at the middle of each side. Vertical 

 view elliptic, generally somewhat umbonate at the 

 middle on each side, and with a minute papilla (rarely 

 absent) on each side near the poles. Cell-wall smooth. 

 Chloroplasts one in each semicell, axile, with a small 

 central pyrenoid. 



Zygospore globose, subgiobose, or oblong-globose, 

 smooth. 



Length 7-12 p. ; breadth 7-12*5 /u; breadth of 

 isthmus 2-5'5/x; thickness 5*5 6*5 ^ ; cliam. zygosp. 

 13-15/1. 



EXGLAXP. - Helvellyn, Westmoreland! (Bissett). 

 Ribblehead, Cowgill Wold Moss on Widdale Fell, 

 Ingleborough, and Greetland, AY. Yorks ! Mickle Fell 

 and Lund's Fell, IS". Y^orks ! Delamere, Cheshire (Roy). 

 Leicestershire (Eoij). Near Chapel Wood and Thursley 

 Common, Surrey ! Keston Common, Kent ! Hants 



(Soy)- 



