133 



1. Cosmarium obsoletum (Hantzscli) Reinsch. 



PL LVI, figs. 1-3. 



Arthrodesmus obsoletus Hantzscli in Kabenh. Alg. 1862, no. 1407 ; Grun. 



Diat. \i. Desm. Ins. Bank. 1865, p. 15, t. 2, f. 28. 

 Cosmarium obsoletum (Hantzscli) Keinsch, Spec. Gen. Alg. 1867, p. 1-42, 



t. 22, D. I, f. 1-4; Lund. Desm. Snec. 1871, p. 38 ; Nordst. Alg. et Char. 



I, 1880, p. 7, t. 1, f. 9 ; Wille, Sydamerik. Algfl. 1884, p. 16, t. 1, f. 33 ; 



De Toiii, Syll. Alo-. 1889, p. 974; West, Alg. W. Ireland, 1892, p. 144 ; 



Alg. Eng. Lake Distr. 1892, p. 724 ; Liitkenmll Desm. Attersees, 1893, 



p. 556 ; Nordst. Index Desm. 1896, p. 186 ; West & Of. S. West, Desm. 



Sino-apore, 1897, p. 164 ; Freshw. Chlorophy. Koli Chang,,1901, p. 87 ; 



Freshw. Alg-. Ceylon, 1902, p. 164. 

 Didymidium (Cosmarium) obsoletum Reinsch. Algenfl. Frank. 1867, p. 110, 



t, 9, f. 5. 



UrsineUa obsoleta Ktintze, Eevis. gen. plant. 1891, p. 925. 

 Cosmarium palustre Turn. Freshw. Alg. E. India, 1893, p. 60, t. 8, f. 65, 



t. 9, f . 29. 

 C. palustre var. ovale Turn, 1. c. t. 9, f. 1. 



Cells of medium size, transversely elliptic, a little 

 broader tliaii long, deeply constricted, sinus narrowly 

 linear with a dilated apex ; semicells semi-elliptic 

 (depressed-semicircular), basal angles submamillate 

 and slightly thickened, apex generally slightly flat- 

 tened. Side view of semicell depressed-globose. 

 Vertical view elliptic, with obtusely conical poles, ratio 

 of axes 1 : 2*1. Cell -wall punctulate (or finely scrobicu- 

 late), sometimes slightly thickened in the centre of the 

 semicells. Chloroplasts axile, each with two pyrenoids. 



Zygospore unknown. 



Length 34-46 ^ ; breadth 42-54 p. ; breadth of isth- 

 mus 15'5-20/x; thickness 20-24 /x. 



ENGLAND.- -Bowness, Westmoreland ! 



\YALES. Yr Orsedd, Carnarvonshire ! 



IRELAND.- -Clogerheen, Kerry ! 



Geogr. Distribution.- -Germany. Austria and Gralicia. 

 Sweden. N. Russia. Poland (var.). Central China. 

 Japan. India. Ceylon. Siam. Singapore. Java. 

 Egypt. New Zealand (var.). Australia. United 

 States. Brazil. 



This species is much more abundant in tropical and sub- 

 tropical countries than in temperate climates, and it exhibits 



