PLATE 4, Confervoidese. 



Figure 



1 . Aphanizomenon Flos-aquce, Morr. a, ordinary filaments ; b, filaments with 



spermatic cells ; c, filament with a vesicular cell (heterocysf) . 



2. Trichormus muscicola, n. sp. a, filament with vesicular cell ; b, ditto, with 



adjoining spermatic cells ; c and d, fragments treated with acid to render the 

 membrane and contents distinct ; e and/, spermatic cells similarly treated. 



3. Sphaerozyga elastica, Ag. 



4. Cylindrospermum catenatum, Ralfs. 



5. Spermosira littoralis, Harv. 



6. Dolichospermum Ralfsii, Thwaites. 



7. Nostoc commune, Vauch. a, ordinary filaments ; b> a single filament in its 



gelatinous sheath ; c and d, fragments with a vesicular cell. 



8. Oseillatoria autumnalis, Ag. , fragment escaped from a sheath b. 



9. Microcoleus repens, Harv.; 5, fragments showing the single sheaths ; c,c?, frag- 



ments treated with sulphuric acid and iodine. 



10. a, by Lyngbya muralis, Ag. 



11. Dasyglcea amorpha, Berk. 



12. a, b, Hassallia ocellata, Berk. 



13. Stfiizosiphon Warreniee, Caspary. a, tuft of filaments; b, c, fragments; d, e, 



decomposing sheaths. 



14. Tolypothrix distorta, Kiitz. 



15. a, Ainactis calcarea, Kiitz. ; b y fragment showing the spiral sheath. 



16. Euactis atra, Kiitz. 



17. Schizothrix Creswellii, Harv. 



18. Rivularia Boryana, Kiitz. 



19. Scytonema Myochrous, Ag. 



20. Arthronema cirrhosum, Hass. 



21. Petalonema alatum, Berk. (Arthrosiphon Grevillii, Kiitz.). a, end of a filament ; 



b, cross section. 



22. a, Calothrix mirabilis, Ag. ; b, junction of filaments. 



