1919] Setchcil-Gard )i( r : Myxophyceae 53 



Repr.). The family of tlio Oscillatoriaceae may be subdivided into 

 several subfamilies, such a.s the Schizotricheae, Lj^ngbyeae, Oscilla- 

 torieae, and Spirulineae. 



Key to the Genera. 



1. TricIiDinos (lo8titiito of a sheath 2 



1. Trichoines provided with a sheath 4 



2. Trichomes twisted into a distinct spiral (Subfamily 1. Spirulineae).,.. 3 (p 53) 

 2. Trichomes straight or, at times, in a loose and irregular spiral (Subfamily 2. 



Oscillarieae) 16. Oscillatoria fp .58) 



3. Dissepiments distinct, spiral, loose 14. Arthrospira (p 53) 



3. Dissepiments indistinct, spiral, loose or tight 15. Spirulina (p 55) 



4. Trichomes solitary within the sheath (Subfamily 3. Lyngbyeae).... 5 (p 67) 



4. Trichomes two to many within a common sheath 



(Sul)family 4. Schizotricheae) 9 (p 83) 



5. Trichomes simple 6 



5. Trichomes branched 8 



6. Sheaths distinct, not diffluent. 7 



6. Sheaths diffluent into an enclosing jelly 17. Phormidium (p 68) 



7. Forming caespitose expansions 18. Lyngbya (p 72) 



■ 7. Forming fasciculatcly tufted layers '. 20. Symploca (p 80) 



8. Filaments free 19 Plectonema (p 78) 



8. Filaments ascending and fasciculate, forming tufted layers 



20. Symploca (p 80) 



9. Trichomes few in a sheath 21. Hydrocoleum (p 84) 



9. Trichomes several to many in a sheath 22. Microcoleus (p 85) 



SUBFAMILY 1. SPIEULINEAE FORTI 



Filaments without a sheath, more or less regularly or irregularly 

 coiled in a laxer or closer spiral. 



Forti, in De-Toni, Syll. Alg., vol. 5, 1907, p. 145. Spirulinmdeac 

 Gomont, Monogr. des Oscill., 1892, p. 248 (1893, p. 116, Repr.) (lim. 

 mut.). 



We have followed Forti {loc. cit.) })oth as to the form of the name 

 of this subfamil}' and as to including Arthrospira as well as Spirulina 

 although Gomont {loc. cit.) includes only Spirulina. From our point 

 of view, both these genera closely approach species of Oscillatoria as 

 will be shown in detail below. 



14. Arthrospira Stizenb. 



Trichomes multicellular, cylindrical, evaginate, loosely and regu- 

 larly coiled, usually of relatively large diameter and large spirals, and 

 comparatively short and with few coils; dissepiments distinct, apices 

 slightly or not at all tapering, terminal cell rounded, calyptra absent. 



