720 University of California Puhlications in Botany [Vol. 8 



Sargassum Johnstonii f . gracile S. and G. 



Basal parts unknown; branches of all orders \'ery slender, long, 

 and wide apart, up to 1 mm. diam. ; leaves filiform ; vesicles narrowly 

 ellipsoidal. 



Cast ashore, Guaymas, Mexico. 



Setchell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 738, pi. 21, 

 fig. 76. 



This differs from the species in being decidedly more slender 

 throughout, much less frequently branched, and in having the branches 

 much longer and more delicate, and in having filiform leaves. In these 

 respects they more nearly coincide with f. laxius but are much more 

 delicate throughout than in that form. The receptacles are young in 

 the specimens at hand. The vesicles are practically the same in form 

 as those of the species. 



15. Sargassum cylindrocarpum S. and G. 



Basal parts unknown ; primary branches and branchlets smooth, 

 terete ; leaves 5-8 cm. long, 3-5 mm. wide, linear-lanceolate, acute, 

 serrate-dentate, midrib percurrent, cryptostomata abundant and con- 

 spicuous ; vesicles 5-8 mm. diam., spherical, smooth, on stipes shorter 

 than the diameter, occupying positions of leaves toward the base of 

 the fructiferous ramuli ; receptacles several times forked, cylindrical, 

 blunt, 1-2 cm. long. 



Cast ashore, La Paz, Lower California. 



Setchell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 738, pi. 21, 

 fig. 77. 



16. Sargassum herporhizum S. and G. 



Fronds 6-8 dm. high, attached at first by a small parenchymatous 

 disk, later the short stipe giving rise to erect primary branches in 

 part and to horizontal branches which in turn develop attaching 

 branches, hapteres, below and to erect branches above ; primary 

 branches slender, terete, smooth, densely clothed with leaves and with 

 scattered secondary branches below and with fructiferous branches 

 above ; lower leaves sublinear, upper linear-lanceolate and acute, lower 

 3-5 mm. broad, upper 1-2 mm. broad, midrib percurrent, margins 

 sparsely denticulate, cryptostomata absent ; vesicles numerous, scat- 

 tered among the receptacles, spherical to subspherical, smooth, rarely 



