1925] SetcheU-Oardner: Melanophyceae 719 



This form stands very close to S. spmuligerum Sond. The leaves 

 are longer and narrower than in that species. There are also other 

 specific differences. 



14. Sargassum Johnstonii S. and G. 



Basal parts unknown ; primary branches relatively robust, terete, 

 smooth, up to 8 dm. long, secondary branches numerous, densely 

 crow^ded with fructiferous ramuli ; leaves narrowly lanceolate, ecostate, 

 margins sparsely denticulate, cryptostomata almost absent, 1.5-2.5 cm. 

 long, 2-4 mm. wide ; vesicles, smooth, narrowly elliptical, merging 

 gradually below into a short petiole, crowned by a mucron or a 

 remnant of a blade, scattered along the fruiting rhachis among the 

 receptacles, 3-5 mm. long, on pedicels shorter than their length ; 

 receptacles single or 2-3 times forked, nearly cylindrical, mostly blunt, 

 with slightly denticulate apices. 



Cast ashore, Georges Island, Gulf of California. 



Setehell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 737, pi. 20, 

 fig. 72 and pi. 21, fig. 80. 



Sargassum Johnstonii is related to *S^. galapagense Grun. but differs 

 in having elongated, long-apiculate vesicles, and slightly denticulate 

 receptacles and in details of leaf characters. 



Sargassum Johnstonii f. laxius S. and G. 



Basal parts unknown; primary branches up to 13.5 dm. long, 

 secondary branches very much less frequent and much longer than in 

 the species ; leaves filiform, 1-2 cm. long, cryptostomata sparse, incon- 

 spicuous ; vesicles subspherical, mostly long-mucronate ; receptacles 

 1-2 times forked, rarely simple, not denticulate. 



Cast ashore at Guaymas, Mexico, 



Setehell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 737, pi. 21, 

 figs. 75 and 81. 



This form differs from the species in the following particulars : 

 the secondary branches and fructiferous ramuli are very much more 

 widely scattered and several times longer, the leaves are narrower, in 

 fact they are filiform, the vesicles are very much shorter, about one 

 and a half times as long as broad, and the receptacles are less branched 

 and rarely, if ever, denticulate at the apices. 



