KEY TO THE GENERA OF THE ATLANTIC 

 COAST. 



OLIVE GREEN ALG^. 

 I. Frond leaf-bearing. 



Main stem and branches cylindrical, bearing 

 globular, stalked minute, air vessels, and 

 narrow, undivided, dotted leaves. General 

 habit arborescent. "Gulf-weed." Sargassum. 



II. Frond, flat, coriaceous or leathery. 

 I. With Midrib. 

 (a.) Frond perforated. Agarum. 



(^.) Frond entire, stem bearing leaflets or 



wings. Alaria. 



2. Without Midrib, 

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



green or brown. "Kelp." Liminaria. 

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



brown, from three to twelve inches 



long. Pimctaria. 



{(.) Frond narrow in proportion to length, 



half-inch wide, eight to twelve inches 



long. Fhyllitis. 



{d.) Frond still narrower and constricted at 



intervals. Scytosiphon. 



