MiCRASTEKIAS. 79 



SCOTLAND. Aberdeen (P. Grant). 



IRELAND. Glencar, Kerry (Archer). 



Gecxjr. Distribution. France. Germany. Austria 

 (forma). G-alicia (forma). Xorway. Denmark. 

 United States. 



Typical j\I. oscitans is exceedingly rare and we have only 

 found it on three occasions. Fig. 4 (on PI. XLI) is a drawing 

 of a semicell from Kirk Fell, Cumberland, which agrees very 

 well with the plant as described by Ralfs. 



American specimens have been described by Wolle with a 

 diameter (breadth) of 150-160 /.*. 



Var. mucronata (Dixon) Wille. (PL XLI, figs. 5, (3.) 



Tetrachastrum mucronatum Dixon in Proc. Dubl. Nat. Hist. Soc. 1859, 



p. 204, t. 1, f . 5-8 ; in Quart. Journ. Micr. Sci. 1859, p. SI, t. 7 ; Arch. 



in Pritcli. Infus. 1861, p. 725. 

 llicrasterias mucronata (Dixon) Rabenh. Flor. Europ. Alg. Ill, 1868, 



p. 187 ; Kirchn. Alg. Schles. 1878, p. 163 ; Cooke in Grevillea, 1881, 



p. 89, t. 141, f. 2 (in part) ; Cooke, Brit. Desm. 1886, p. 53, t. 20, f. 1 ; 



De Toni, Syll. Alg. 1889, p. 1112 ; West, Alg. N. Wales, 1890, p. 286 ; 



Alg. W. Ireland, 1892, p. 133 ; Alg. Eng. Lake Distr. 1892, p. 722 ; 



Roy & Biss. Scott. Desm. 1893, p. 174; Xordst. Index Desm. 1896, 



p. 177 ; West & G. S. West, Alg. S. England, 1897, p. 484. 

 M . oscitans Ealfs var. mucronata (Dixon), Wille, Norges Ferskv. Alg. 1880, 



p. 21, t. 1, f. 3 ; Turn. Freshw. Alg. E. India, 1893, p. 88 ; West & G. S. 



West, Alga-fl. Yorks. 1900, p. 65. 

 Helierella mucronata Ktintze, Revis. gen. plant. 1891, p. 899. 



Cells proportionately longer than in the type, with 

 the sinus more closed ; lateral lobes larger and some- 

 what inflated, lateral angles generally furnished with 

 two blunt teeth, and often with a third tooth above 

 those at the angles ; polar lobe flattened at the apex, 

 and sometimes broadly retuse, lateral angles down- 

 wardly curved and generally furnished with a single 



v O </ O 



blunt tooth ; with the incisions below the polar lobe 

 commonly smaller than in the type. Vertical view 

 elliptic or elliptic-rhomboid, with acute poles. 



Length 130-156 /x,; breadth 104-131 p; breadth of 

 polar lobe 73-84 f.i ; breadth below polar lobe 58-64 /u ; 

 breadth of isthmus 25-33 ji ; thickness 59-62 p. 



EXGLAND. Borrowdale, Cumberland ! Near Winder- 



