COSMARIUM. 119 



Cells somewhat small, about as long as broad or a 

 little longer, deeply constricted, sinus almost linear; 

 semicells truncate-pyramidate or widely semihexagonal, 

 basal angles rounded or retuse-truncate, lateral margin s 

 (which in some cases are really the upper lateral 

 margins) biundulate, with two hollows and one crest, 

 apical angles rounded, apex widely truncate, straight 

 or very slightly concave. Side view of semicell sub- 

 circular. Vertical view elliptic, with a broad median 

 tumour on each side, ratio of axes about 1 : 1'7. Cell- 

 wall coarsely punctate. Chloroplasts axile, each with 

 a large central pyrenoid. 



Zygospore unknown. 



Length 61-64-8 /x; breadth 50'4-60/z; breadth of 

 isthmus 16*o-21 /LI ; thickness 30 //,. 



SCOTLAND.- -Fintray Hills, Stirling (Roy $ Bissett). 



Geogr. Distribution.- -Italy. Galicia in Austria. 

 United States (var.). 



C. orthogonum is closely allied to (7. Ndgelianum, of which 

 species we have in the past regarded it merely as a variety. 

 We have not ourselves examined any specimens of it, but 

 Messrs. Roy and Bissett have recorded it as occurring in 

 Scotland. Delponte's figures, which we have reproduced, 

 indicate a considerable variability in the form of the semicells. 



*/ 



Consult remarks on p. 15 under C. Ndgelianum. 



128. Cosmarium Capitulum Roy & Biss. 

 (PL LXXI, fig. 18.) 



Cosmarium Capitulum Koy & Biss. Jap. Desm. 1886, p. 195, t. 268, f . 9 ; 

 De Toni, Syll. Alg. 1889, p. 939; Gutw. Flor. Glon. Okolic LAVOWU, 

 1891, p. 45, t. 1, f. 24 [forma] ; Eichler in Pamietnik Fizyjogr. 

 Warszawa, 1895, p. 59 ; Nordst. Index Desm. 1896, p. 72 ; Larsen, 

 Freshw. Alg. E. Greenland, 1904, p. 83. 

 Ursinella Capitula Ktintze, Eevis. gen. plant. 1891, p. 924. 



Cells small, a little broader than long, very deeply 

 constricted, sinus widely open outwards, but narrowed 

 and almost acuminate at the apex; semicells elliptic- 

 obsemicircular, lower part of lateral margins convex, 

 apex convex, angles produced into stout rounded 

 mamillse with a slight upward direction. Side view of 



