Tin: MvnixE ahj.f. of new i:nt.land. 185 



AirriFICIAL KEY TO GENERA. 



NoTK. — Tlu' t"»»llt»\vinj; key is iiitoiulod to citable persons who arr not at all ac<inaiiit«»l 

 ■with our sta-\viT<ls to astertuiu with a partial dej^ree of accuracy the genera to whiih 

 hlR'ciujeus which they may collect arc to bo referred. For this purpose the characters 

 used are, as far as i)ossible, those which can bo seen by the naked eye, but, as in many 

 cases, the generic distinctions absolutely depend on microscopic characters, one must 

 not cxi>ect to be able to recognize all of our forms without making a more or less care- 

 ful microscopical examination, especially in the ca8e of the Cryptophycea and Pkao- 

 ttporecF. It should of course be understood that the key is entirely artificial, and does 

 not represent the true botanical relations of our genera ; since in many cases the char- 

 acters refer only to species of our Atlantic coast and would mislead astuilent having 

 a si>ecimeu from other waters. 



1. Color hlnisli or puriilish green,* algop of small size, usually more or 



less gelatinous - . . . ( Cryto2)hycc(v) 5 



2. Color grass green 18 



3. Color from yellowish brown to olive green or nearly black 2G 



4. Color red or reddish purple, rarely blackish, in fading becoming at 



times greenish {Floridcw) 48 



5. Cells arranged in fdaments 



Cells in colonies, but not forming filaments G 



C. Cells grouped in twos or some multiple of two 7 



Cells solitary, not adherent in twos 8 



7. Groups free, not united with one another by a gelatinous envelope. 



Chroococcus. 



Groups united by a gelatinous substance so as to form irregularly- 

 shaped colonies Glaocapsa, 



Groups united by a gelatinous substance so as to form colonies of a 

 dendritic shape EntophysaVis. 



8. Cells imbedded in a gelatinous substance, forming colonies of indefi- 



nite shape Poll/cyst is. 



Cells imbedded in a gelatinous mass, Avhich forms at first ovoidal ajid 

 afterwards net-shaped colonies Clathrocystis. 



9. Filaments ending in a hyaline hair IG 



Filaments not ending in a hair 10 



10. Fihiments i)rovided with heterocysts f 11 



Filaments destitute of heterocysts 12 



11. Fihiments with a thin gelatinous sheatli, spores not adjacent to the 



hetero<vsts Xodularia. 



• Our marine species of ClathrocyMtUi and the genus Begyxatoa are exceptions. The 

 former is pinkish, and covers the mud and alga* between tide-marks with n very fine 

 i^elatinous film. The 8i>ecies of Jiiggiatoa are whitish to the naked eye, and form very 

 delicate films over decaying algje. 



t Vid. page 11. 



