KEY TO THE GENERA. 129 



5. Frond consisting of visibly articulated, or 

 jointed filaments. 

 Slender or robust, branching or forking ; 

 filaments showing alternately white and 

 red, or light and dark bands. 



Cera7Jiiiim. 



6. Frond stiff, wiry, black. 

 Intricately and irregularly branched, some- 

 times bleached white. Ahnfeltia. 



7. Frond stony and hard. 



Purple to white. Corallina. 



IV. Frond capillary. 



(Composed of a single series of cells 

 placed end to end). 

 I. Cells long. 

 Frond divided by regular, narrow forkings, 

 fan-shaped, level topped ; color pale, 

 delicate pink. Griffithsia. 



2. Cells short. 

 Plants mostly small, often shaped like 

 a miniature shrub ; much branched, 

 final divisions as fine as cobweb ; color 

 brilliant red or pink, the most beautiful 

 of plants. Callithamnion. 



