30 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



2. Filaments fiirnislied with lieterocysts 10 



Filameuts destitute of lieterocysts 3 



3. Filaments spirally twisted Spirulina. 



Filaments not twisted 4 



4. Filaments without a distinct sheath 5 



Filaments formed of one or more colored trichomata contained in a 



transparent sheath 6 



o. Cells bluish green or purple Oscillaria. 



Cells colorless, or filled with minute black grains Beggiatoa. 



G. Sheath containing several trichomata Microcoleus. 



Sheath containing only one trichoma Lynghya, 



7. Filaments free, forming tufts of indefinite extent Calothrix. 



Filaments united by a more or less firm gelatinous substance, 



frond of definite shape and extent 8 



8. Heterocysts basal, i. e., placed at the base of the principal filaments 



and branches 9 



Heterocysts intercalary Hormactis* 



9. Frond hemispherical or vesiculose, filaments radiating from the 



base Rivularia. 



Frond plane, filaments parallel Isactis. 



10. Filaments destitute of a sheath Sphcerozyga, 



Filaments consisting of a trichoma in a sheath Nodular ia, 



SPH^EOZYGA, Ag. 



(From atpaipa, a sphere, and C,vyo^, a yoke. ) 



Filaments free, destitute of sheath. Spores produced in the cells adja- 

 cent to the heterocysts. 



S. Carmichaelii, Harv., Phyc. Brit., PL 113 a. {Cylindrospermum^ 

 Kutz., Spec. Alg., p. 294. — Andbaina marina^ Breb.). PL I, Fig. 3. 



Filaments flexuous, densely interlaced, forming slimy bluish-green 

 expansions, cells cylindro-spherical, about .0035™™ in diameter, dimin- 

 ishing in size towards the end of the filament, terminal ceU pointed. 

 Heterocysts several in each filament. Spores oblong, usually one on 

 each side of heterocyst, about .018™™ in length when ripe, rather more 

 than twice as long as broad, at first green, then yellowish. 



Noank, Conn.; Wood's Holl, Gloucester, Cambridge, Mass.; Europe. 

 Summer. 



Probably a common alga along our -whole coast in midsummer and autumn on 

 decaying algai, looking like a shining emerald-green film. It occurs most frequently 

 on the suiface, but is also found at the depth of several feet. In his work on the 

 Fresh-water Alg£e of America, Prof. H. C. Wood, jr., mentions the j)resent species as 

 occurring at Camden, N. J. We cannot, however, agree with him in placing it in 



i 



