REVISED LIST OF MARINE ALGM. 129 



8. Filaments provided with heterocysts 9 



Filaments destitute of heterocysts 10 



9. Filaments with a thin gelatinous sheath, spores 



not adjacent to the heterocysts ... J^odidaria 

 Filaments without a sheath, spores next to the 

 heterocysts . . ... ... ... ... Anab&na 



10. Filaments with a gelatinous sheath 12 



Filaments without a gelatinous sheath ... ... 11 



11. Filaments spirally twisted Spirulina 



Filaments not spirally twisted ... ... Oscillaria 



12. Filaments free Lyngbya 



Filaments adherent in meshes ... ... Symploca 



Filaments united into a membranous layer 



Phormidiitm 

 Filaments united in bundles and surrounded by 

 a general gelatinous sheath ... Microcoleus 



13. Filaments free... ... ... ... ... Galothrix 



Filaments imbedded in a mass of jelly ... Bivularia 



14. Fronds unicellular 15 



Fronds multicellular 17 



15. Cells free 16 



Cells united into a branched spongy frond Codium 



16. Cells large, filamentous, pinnately branched Bryopsis 

 Cells very long, cylindrical with irregular or sub- 



dichotomous branches, spores large, solitary, 



in special lateral or terminal cells . . . Vaucheria 



17. Minute endophytic algse, growing in the 



cell- walls of Pylaiella ... ... Entoderma 



Algae not endophytic 18 



18. Fronds tubular Enteromorplm 



Fronds membranaceous 19 



Fronds filamentous 21 



19. Fronds formed of a single layer of cells 20 



Fronds composed of two layers of cells ... Ulna 



