PENIUM. 



103 



Its true position is in the Tribe Cosmariese, but it cannot be 

 regarded as an elongated Cosmarium, neither can it be 

 reasonably placed in a distinct genus. Until more is known 

 concerning its structure it is best left in the genus Peni'inn, 

 particularly as its zygospore is still unknown. 



The chloroplasts are very variable, especially when the 

 plant occurs in large quantity. The longitudinal ridges are 

 most irregular, often being entirely absent, and the chloro- 

 plast of each semicell sometimes becomes quite parietal. We 

 have observed a few specimens in which it was a parietal 

 spirally-twisted band, similar to the chloroplast of certain 

 species of Spirotsenia. 



There are numerous varieties of it, most of which are 

 British. 



Forma major Lund. (PL X, fig. 4.) 



Penium minvtum forma major Lund. Desm. Suec. 1871, p. 87; Eacib. 

 Norm. Desm. Polon. 1885, p. 61 ; West, Alg. W. Ireland, 1892, p. 129. 



Length 170-270 /*; breadth 12'5-lS/u. 

 SCOTLAND. Harris, Outer Hebrides ! 

 IRELAND. Ballynahinch, Galway ! 

 Geor/r. Distribution. Austria. Sweden. 



Forma minor Eacib. (PI. X, fig. 3.) 



Forma minor Racib. Nonn. Desm. Polon. 1885, p. 61 ; West, Alg. W. 

 Ireland, 1892, p. 129. 



Length 60-85 /u ; breadth 5-5-ll'5ju,; breadth of 

 apex 4' 5-9 ,11. 



SCOTLAND. Sligachan in Skye, Inverness ! 



IRELAND. Cromagloun, Kerry ! 



Geor/r. Distribution. Poland. West Africa. 



Var. gracile \Ville. (PI. X, fig. 6.) 



Var. gracile Wille, Norges Ferskv. Alg. 1880, p. 51, t. 2, f. 33 ; Racib. 

 Nonn. Desm. Polon. 1885, p. 60 ; West, Alg. N. Wales, 1890, p. 284 ; 

 Alo-. W. Ireland, 1892, p. 129 ; West & G. S. West, Welw. Afric. Freshw. 

 Alg. 1897, p. 78 ; Some N. Amer. Desm. 1896, p. 237 ; Freshw. Alg. 

 Ceylon, 1902, p. 136. 



Cells elongated, 14-20 times longer than their 



O 



diameter. 



Length 110-220 /it; breadth 7'5-12//. 

 WALES. Capel Curig, Carnarvonshire ! 



