NOSTOC. 293 



forms, most of them being spherical but many of them angular. 

 The filaments are minute, much curved, and the cells are 

 spherical or slightly oval. It is one of the most distinct and 

 beautiful species of the genus. In the smaller specimens, 

 there is but a single thread, which curves in an elegant manner 

 throughout the frond. 



9. NOSTOC C^ERULEUM Lyngb. 



Plate LXXVL Fig. 11. Plate LXXV. Fig. 10. 



Plate LXXIV. Fig. 1. 



Char. Frond solitary, small, globose, solid, fluid within, at 

 length vesicular, mostly pale blue, sub-pellucid. Filaments 

 large, elegantly moniliform, much curved. 



Nosloc cceruleum Lyngb., Hydroph. p. 201. No. 6. 768. /3; 

 Grev. Crypt. Fl. t. 131. ; Hook. Brit. Flor. p. 400. ; 

 Harv. in Manual, p. 185. ; Meneghini, Monographia 

 Nostochinearum Italicarum, p. 111. 



Hob. In flowing water or in very moist places attached to 

 mosses, near Calender : Dr. Greville. Co. Antrim ; near 

 Wicklow : Mr. D. Moore. Pass of Lerry : Dr. Greville. 



This species in its dried state might be readily passed over 

 as Nostoc commune in the first period of its growth, the fila- 

 ments of N. cceruleum according exactly with those of that 

 species. Notwithstanding the difference in its colour, and 

 perhaps in its habit also, I am not perfectly assured that it 

 is really distinct. The larger size of the filaments will serve 

 to distinguish it from Nostoc sphcericum, . which in form it 

 resembles, as well as the difference in its colour, and its 

 greater mucosity, which causes it to adhere closely to paper. 







10. NOSTOC MACROSPORUM ? Menegh. 



Plate LXXIII. Figs. 1, 2. 

 Char. Frond minute, solid, spherical, ceruginous green. 



