N08TOC. 283 



NOSTOC CALCICOLA, Ag. 



Not separable from N. commune, Ag. ; a condition of it. 

 Moist rocks, South Carolina. 



NOSTOC COMMUNE, Vaucll. 



In connection with this form, read note above under 

 generic characters. 



Syn. Tremula nostoc, Linn. ; Nostoc ciniflonum, Born, and Thur. ; 

 N. foliaceum, Ag. ; N. arctum, Kg.; N. littorale. Kg.; N. 

 prismaticum, Ces. ; N. rugosum. Kg. ; N. salsum. Kg. 



Frequent on wet ground, rocks, etc. 

 Diameter of filaments, 5-6 yw. 



Plate CXCVII, fig. 8, a not unusual form of a thallus ; 

 fig. 9, filaments separated from the thallus and greatly en- 

 larged ; figs. 10, 11, cells of filaments separated, and young 

 filaments developing; figs. 12-14, filaments somewhat ad- 

 vanced, commencing to branch ; fig. 15, young filaments 

 uncoiling after the manner of some Oscillaria ; figs. 16, 17, 

 two filaments with one part unchanged, moniliform, the 

 other end widened and changed, in character with the others. 



NOSTOC SPHAEBICUM, Vauch. 



Fronds very variable in size from that of poppy and mus- 

 tard seed to that of peas; gregarious, usually olive or yel- 

 lowish brown, more rarely somewhat aeruginous ; periderm 

 firm, brownish. 



Diameter of filaments, 4-5-6 //. 



Frequent on damp rocks, in large numbers. 

 Plate CXCVII, figs. 18-20, sizes as they vary with age. 



NOSTOC RUPESTRE, Kg. 



Fronds same as the last ; the forms that receive this appel- 

 lation appear to be merely another growth, or another gen 

 eration of fronds ; primarily the moniliform filaments are 

 sheathless as figs. 21-23, then they become sheathed as figs. 

 24, 25. Next the teguments dissolve, and the young are 

 scattered, producing such forms as figs. 26-30, which con- 

 stitute the N. rupestre, Kg. , a form which embraces also N. 

 macrosporum, Menegh. ; N. coriaceum, Vauch. ; N. verrucosum, 

 Vauch. ; N. tenuissimum, Rab. ; N. microscopicum, Carm. ; N. 

 gregarium, Hantzsch. ; Hormosiplion farfuraceus, Kg.; H. 

 macrosiphon, Kg. ; and others, all of which are merely differ- 

 ent stages of growth. 



