182 BRITISH DESMIDIACE^. 



Cosmarium protractum (Nag.) Be Bary, Conj. 1858, p. 72 ; Arch, in 

 Pi-itch. Infus. 1861, p. 733 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 172 ; 

 De Toni, Syll. Alg. 1889, p. 1028 ; Anderss. Sverig. Chlor. 1890, p. 17 ; 

 Eoy & Biss. Scott. Desm. 1894, p. 172 ; Nordst. Index Desm. 1896, 

 p. 206; West & G. S. West, Some Desm. U. S. 1898, p. 309; Him, 

 Desm. Filmland, 1903, p. 11, t. 1, f. 10 ; Larseii, Freshw. Alg. E. Green- 

 land, 1904, p. 87. 



Didymidium (Cosmarium) protractum Eeinsch, Algeiifl. Frank. 1867, 

 p. 120 [a majus et j3 minus~]. 



Cosmarium ornatum E-alfs var. protractum Wolle, Desm. U. S. 1884. 

 p. 82, t, 49, f. 22 [figure poor] ; Borge, Sverig. Chlorophy. II, 1895', 

 p. 20. 



C. ornatum var. minor Wolle, 1. c. t. 17, f. 29 [figure poor]. 



C. ornatum var. polonicum Eacib. Nonn. Desm. Polon. 1885, p. 72, t. 11, 

 f. 3 [figure poor] ; Gutw. Flor. Glon. Okolic Tarnapola, 1894, p. 99. 



C. Turpinii Breb. var. polonicum (Eacib.) Schmidle, Lappmark Siiss- 

 wasseralgeii, 1898,, p. 39. 



Cells somewhat small, about as long as broad or 

 slightly longer, very deeply constricted, sinus narrowly 

 linear with a slightly dilated extremity; semicells three- 

 lobed, with a subrectangular incision between the apical 

 lobe and each lateral lobe, lateral lobes rather narrow 

 and rounded, apical lobe short, with rounded angles 

 and a slightly retuse apex ; lobes granulate, granules in 

 more or less distinct decussating oblique series, be- 

 coming reduced in size towards the large granulated 

 central protuberance, the granules of which are 

 arranged in concentric rings. Side view of semicell 

 ovate, with a protuberance on each side near the base. 

 Vertical view rather narrowly elliptic-oblong, with a 

 granulated protuberance at the middle on each side, 

 apex of semicell rectangular-oblong with rounded 

 angles. Chloroplasts axile, with two pyrenoids. 



Zygospore unknown. 



Length 34-45 ^u; breadth 3 3-42 ^t; breadth of apex 

 16-19 jji ; breadth of isthmus 9-12 p. ; thickness 

 19-5-24^. 



ENGLAND.- -Sutton Park, Warwickshire! 



SCOTLAND.- -Tableland above the head of Grlen Cal- 

 later, Aberdeen (Roy $ Bisseti). 



Geogr. Distribution.- -Germany. Galicia in Austria. 

 Poland. Norway. Sweden. Finland. United States. 



This species is well characterized by its strongly projecting 

 apex,, which gives the semicells a three-lobed appearance. In 



