KEY TO THE GENERA. 131 



5. Fronds regularly foj^king, thin, narrow ; sides of 

 lobes parallel, ends rounded. 



{a.) Dull red, not adhering. Rhodyi7ienia. 



{b.) Brilliant red ; interrupted midrib of darker 

 color, or fruit dots scattered over the 

 surface ; adheres. Stenogratnma. 



II. Frond f attened or compressed. 



I. Frond pinnately branched. 



{a.) Frond narrow, dense, hard, dark red. 

 Primary branches, alternate or forking ; 

 secondary, short, tapering to both ends, 

 pinnate. Prionitis lanceolata. 



(b.) Frond narrow, cartilaginous, divided into 

 several branches ; j^innae and pinnulae, 

 alternate, blunt at apex ; dull purple. 



Faiirencia. 



{c.) Pinnae, arranged on the edges of the 

 main stem and long branches, short, the 

 opposite ones unlike. Ptilota. 



(d.) Frond very narrow, horny when dry; main 

 branches irregular ; pinnae and pinnulae 

 exactly opposite, with wide rounded 

 axils, ultimate pinnae tapering to both 

 ends ; purple, often faded. Gelidium. 



