368 Marine Algoe of Beriuick-on-Tiveed. 



Artificial Key to the Genera of Bemvick Marine Algce. 



Adapted, with his sanction, from Prof. Farlow's Key to the 

 Marine Alg^e of New England. 



Note. — " As far as possible, the characters used are those which can be 

 seen by the naked eye, but in many cases the generic distinctions ab- 

 solutely depend on microscopic characters. It should of course be under- 

 stood, that the key is entirely artificial, and does not represent the true 

 botanical relations of our Genera," moreover, in many cases the characters 

 given refer only to the species found at Berwick.* 



1. Colour, bluish or purplish green f; Alga? of small size, usually more or 



less gelatinous ... ... ... (Ct/anophycece.) 5 



2. Colour, grass green. ... ... ... ... ... 17 



3. Colour, from yellowish brown to olive green or nearly black. ... 25 



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

 times greenish. ... ... ... (Rhodophycece.) 50 



5. Cells arranged in filaments. ... ... ... ... 7 



Cells in colonies, but not forming filaments. ... ... 6 



6. Cells grouped in twos or some multiple of two. Glceocapsa. 

 Cells solitary, small, oval, imbedded in a gelatinous substance forming 

 colonies of indefinite shape. ... ... ... Polycystis. 



Cells large, wedge-shaped or spherical, united into hemispherical or 



irregularly shaped colonies. ... ... Dermocarpa. 



7. Filaments ending in a hyaline hair. - ... ... ... 15 



Filaments not ending in a hair. ... ... ... 8 



Plant parasitic in the chalky shells of molluscs, forming bluish-gray 

 stains on them. ... ... ... ... Mastigoeoleus. 



8. Filaments provided with heterocysts. X ■•• ••• ••• 9 



Filaments destitute of heterocysts. ... ... ... 11 



* The genera Ascocyclus, Actinococcus, and Choreocolax, which were 

 added to the Berwick flora after this List was in the printer's hands, are 

 not included in this Key. 



f Glceocapsa crepidinum, Goniotrichum elegans, Dermocarpa violacea, and 

 D. rosea, are exceptions, the first is yellowish brown, the others purplish 

 pink. 



% " Besides the ordinary cells, we find in many species of Nostochinece, a 

 second kind of cell, distinguished from the others by its glassy appearance 

 and its yellowish or brownish rather than bluish-green colour. They are 

 called heterocysts, and are found sometimes scattered amongst the other 

 cells, sometimes at the end of the trichomata, their position often serving 

 as a generic character." 



