NOSTOC. 289 



of -ZV. commune, but the filaments are different, being much 

 smaller in size, although, like those of N. commune) distinctly 

 moniliform. 



3. NOSTOC FOLIACEUM Ag. 

 Plate LXXVI. Fig. 2. 



Char. Frond membranaceous, erect, plaited, olive green. 

 Filaments slender, copious, moniliform. Enlarged globuli 

 numerous. 



Nostoc foliaceum Ag., Syst. p. 19. ; Harv. in Hook. Br. 

 Flora, ii. p. 399. ; Harv. in Manual, p. 184. ; Meneghini, 

 Monographia Nostochinearurn Italicarum, vol. v. p. 18. 

 serie ii. delle Memorie della R. Academic delle Scienze 

 di Turino. 



Hob. On clayey ground kept constantly damp by the 

 oozing of water, Appin : Capt. Carmichael. Ireland : 

 Mr. Moore. 



" This species is easily distinguished both by its appearance 

 and station from Nostoc commune, to which it seems similar, 

 as respects certain external characters. It never swells up 

 into the form of a vesicle ; the structure, altogether uniform, 

 extends as a membrane, and rises up by moisture into plicated 

 lobes : it grows on stones, and is evolved, the winter scarcely 

 being ended, when Nostoc commune has not yet appeared. "- 

 Menegh. The difference in the size of the filaments of Nostoc 

 commune and- N. foliaceum is perhaps the only character 

 whereby the two species can at all times be discriminated, 

 the threads being much smaller in the latter species. 



4. NOSTOC SPHJERICTJM Vauch. 

 Plate LXXVI. Fig. 5. 



Char. Frond small, globose, densely aggregated, solid, smooth, 

 olive green, watery within. Filaments small, moniliform. 



Nostoc sph&ricum Vauch., Conf. p. 223. pi, xv. f. 2. 



u 



