EXPLANATIONS AND REFERENCES, 

 PLATE CXCVII. 



PAGE. 



Fig. 1. NOSTOC VERRFCOSUM, a frond, ..... 2S5 



" 2. moniliform filaments from a frond, . 285 



Figs. 3, 4. NOSTOC COERULEUM, N. minutissimum, Kg., . (279), 284 



Fig. 5. NOSTOC PRUNIFORME, well developed forms, . . . 284 



Figs. 6, 7. " " filaments from a frond . . 284 



Fig. 8. NOSTOC COMMUNE, a not infrequent form of thallus, . . 283 



" 9. Normal form of filaments, ..... 283 



Figs. 10, 11. Cells of filaments separated and developing young plants. . 283 

 Fig. 12-15. Forms of newly developed plants, .... 283 



Figs. 16, 17. Two young filaments, in part developed, in part unchanged, 



moniliform, ...... 283 



Fig. 18-20. NOSTOC SPHAERICUM, natural sizes as they vary with age, . 283 

 " 21-23. NOSTOC RUPESTRE, not separable from the last, but more fully de- 

 veloped. Filaments primarily without sheaths, 283 



Figs. 24, 25. A more matured frond, filaments have formed sheaths, . 283 

 Fig. 26-30. Forms which constitute the N. rupestre, Kg., embracing also N. 



macrosporum, Menegh.; N. coreaceum, Vauch.; N. verruco- 

 sum, Vauch.; N. tenuissi,mum, Rab.; N. microscopicum, 

 ('arm.; N. gregarium, Hantzsch.; Hormosiphon furfuraceus, 

 Kg., and others, all of which are merely different stages 

 of growth, ...... 283 



" 31. A multiplication of Nostocs, ..... 278 



" 32. NOSTOC FLAGELLJFORME, from specimens from Texas, . 285 

 Figs. 33, 34. NOSTOC ALPINUM, Kg., N. eristatum, Bail.; N. parmelioides, Kg., 285 

 Fig. 35. NOSTOC MUSCORUM, ...... 282 



