KEY TO THE GENERA OF THE ATLANTIC 

 COAST. 



OLIVE GREEN ALG^. 

 I. Frond leaf- hearing. 



Main stem and branches cylindrical, bearing 

 globular, stalked minute, air vessels, and 

 narrow, undivided, dotted leaves. General 

 habit arborescent. "Gulf-weed." Sargassufn. 



II. Frond, flat, coriaceous or leathery. 

 I. With Midrib, 

 (a.) Frond perforated. Agarmn. 



{p.) Frond entire, stem bearing leaflets or 



wings. Alaria. 



2. Without Midrib. 

 («.) Frond thick, leathery and large, dark olive 



green or brown. "Kelp." Limifiaria. 

 {b.) Frond thinner and smaller, light green or 



brown, from three to twelve inches 



long. Puncfaria. 



(<r.) Frond narrow in proportion to length, 



half-inch wide, eight to twelve inches 



long. Phyllitis. 



{d.) Frond still narrower and constricted at 



intervals. Scytosiphon. 



