COSMAEIUM. 221 



This variety is distinguished bv the bidentieulate crenations 



J o J 



of the lateral margins, and in this respect it closely resembles 

 C. subcrenatum var. divaricatum \Ville and C. subcostatum 

 forma minor W. & Gr. S. West. It appears to be a connecting- 

 form between C. KjeUmani and C. subcrenatum. 



Var. grande \Yille. (PL LXXXV, fig. 15.) 



C. KjeUmani subsp. grande "\Ville, Ferskv. Alg. Nov. Semlj. 1879, p. 43, 

 t. 12, f . 33 ; Boldt, Desm. Gronlancl, 1888. p. 24 ; Borge, Siber. Chlor. 

 1891, p. 13; Roy & Biss. Scott. Desm. 1894, p. 104; West & G. S. 

 West, Alg. S. England, 1897, p. 489 ; Alga-fl. Yorks. 1900, p. 76 ; Borg. 

 Freshw. Alg. Faeroes, 1901, p. 227 ; West & GK S. West, Scott. Freshw. 

 Plankton, I, 1903, p. 527. 



Larger than the type, with the semicells proportion- 

 ately a little higher, with relatively more granules 

 (about 8 marginal on each side) ; granules forming 

 the 5 vertical series covering the central tumour more 

 pronounced ; chloroplasts with two pyrenoids. 



Length 45-52 /x ; breadth 40-47 JJL ; breadth of isth- 

 mus 13-1 6 /x; thickness 18-26 ^. 



EXCILAXD.- -Baildon Moor, W. Yorks ! Eanmore 

 Common, Surrey ! 



SCOTLAND.- -Bourtie, Aberdeen (It"'/ $ Bissetf). 

 Plankton of Loch Laxadale, Harris, Outer Hebrides ! 



Geoc/r. Distribution. Bornholm. Faeroes. Nova 

 Zembla. Greenland. Siberia. 



This variety is distinguished by its larger size, its propor- 

 tionately longer cells, and the two pyrenoids in each chloro- 

 plast. AVe do not attach too much importance to the latter 

 character, even though the type form of C. KjeUmani has 

 only one central pyrenoid in each semicell. The larger size 

 of the c.ell may possibly account for the duplication of the 

 pyrenoids. 



197. Cosmarium humile (Gray) Xordst. 

 (PI. LXXXV, figs. 16-18.) 



Euastrum (Cosmarium} eel at inn Gray, Moiiogr. loc. Conj. Montpellier, 1884, 

 p. 59, t. 1, f. 17. [This is not C. uelatum Ealfs, 1848.] 



Euastrum (Cosmarium} humile Gay, Xote Conj. du inidi de France, 1884, 

 p. 336. 



Cosmarium humile (Gay) Xordst. in De Toni, Syll. Alg. 1889, p. 965; 



