COSMARIUM. 271 



Didumidium (Cosmarium) tetraophthalmuni Reinsch, Algeiifl. Frank. IM>~, 



p. 121. 



Cosmarium tetraoplithalinum forma Lund. Desm. Suec. 1871, p. 27. 

 C. tetraophthalmum Bivb. var. LundeUii Wittr. Gotl. Ol. sotv. Alg. 1872, 



p. 56; Xordst. Desm. Arctoae, 1875, pp. 17, 4-0; Desm. Gronlaiid, 1885, 



p. 7 ; Boldt, Desm. Groiiland, 18S8, p. 28 ; Gutw. Flor. Glon. Galic. 



1890, p. 14; Anderss. Sverig. Chlor. 1890, p. 14; Borge, Chlorophy. 



Xorska Finmark. 1892, p. 9 ; West, Alg. W. Ireland, 1892, p. 152 ; Alg. 



Eiigi. Lake Distr. 1892, p. 726 ; Gutw. Flor. Glon. Okolic Tarnapola, 



1894, p. 90; Boy & Biss. Scott, Desm. 1894, p. 176; West & G. S. 



West, Alg-. S. England, 1897, p. 488 ; Alga-fl. Yorks. 1900, p. 82 ; 



? Him, Desm. Filmland, 1903, p. 13, t. 1, f. 16 ; Borge, Beitrage Alg. 



Schwedeii, 1906, p. 30. 

 Ursinella tetraophthalma Knntze, Revis. gen. plant. 1891, p. 925. 



Cells large, about 1^ times as long as broad, deeply 

 constricted, sinus narrowly linear with a dilated ex- 

 tremity ; semicells pyramidate-ovate, basal angles very 

 broadly rounded, sides slightly convex, extreme apex 

 truncate and the apical angles rounded ; cell-wall 



o'rannlate and between the granules distinctly and 



. ^ 



finely punctate, with 12-14 large, rather flattened 

 granules along each lateral margin, extreme apex 

 smooth, granules within the margin large and more or 

 less scattered (with indications of both oblique and 

 concentric arrangements), with a gradual reduction of 

 granules towards the centre of the semicell, where they 



-3 tj 



are quite small, and also with a considerable reduction 

 of the granules within the smooth apex. Side view of 

 semicell almost circular. Vertical view elliptic, ratio 

 of axes about 1 : T4, poles and within the poles 

 strongly granulate, also granulate within the sides, at 

 the middle of each side and in the centre destitute 

 of granules. Chloroplasts axile, each with two large 

 pyrenoids. 



Zygospore ellipsoid, furnished with numerous mamil- 

 late warts (about 32 visible at the periphery), each of 

 which is terminated by a short (often curved), simple 

 spine. 



Length 90-1 20 /x; breadth 60-86 ^ breadth of 

 isthmus 18-30/x; thickness 42-51 /j, ; cliam. zygosp. 

 without spines 120-137 //,, with spines 145-163 p,. 



EXGLAXD.- -Cumberland ! Westmoreland! (Zu//fx). 

 Lancashire ! AY., X., and E. Yorks ! Cheshire (Ecnj). 



