242 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



La Paz, and Turner's Island. It has characteristically very small, broad, 

 unsymmetrical leaves, and vesicles with a conspicuous, irregularly toothed 

 crest which may extend into a margin around the edges of the bladder. 

 The small size of the upper leaves and the shortness of this crest distin- 

 guish this plant from the other members of the group. 



The receptacles of Sargassurn lapazeanum are quite distinctive, being 

 variously and rather conspicuously dentate in both sexes. The antheridial 

 receptacles are commonly smaller in diameter and more openly branched. 

 In both cases the heteroclyte character is more or less conspicuous. The 

 variation is of such a nature as easily to include the obviously similar speci- 

 mens given the names S. Bryantii and S. insulare in the 1924 account. 

 The former has somewhat flattened receptacles, but the type specimen is 

 oogonial. From the study of the sexual dimorphism of receptacles in these 

 plants it is clear that the above character used to distinguish S. Bryantii is 

 one of sexual variation. The heteroclyte cyme condition is also variable, 

 and the gradient is such that it seems impossible to set apart the type speci- 

 men of S. insulare from the two afore-mentioned species. The names Sar- 

 gassurn Bryantii and S. insulare become synonymous with S. lapazeanum. 



Sargassurn acinacifolium is represented by three mature specimens, 

 two oogonial (Brand. 2, Guaymas; J. 75, San Francisquito Bay, June) 

 and one sterile (MacDougal, Port Libertad, May). This species may be 

 distinguished fairly well on the basis of the vesicles, most of which have 

 merely a simple apicula about 0.6 as long as the bladder, unflattened or 

 not conspicuously so. The smoothness of the oogonial receptacles seems 

 generally reliable as does also the branching habit, which is much more 

 deliquescent than in the two following members of the group. These char- 

 acters are sufl!icient for present segregation and they may be found to 

 hold, though relationship with the other members of the group is very 

 close. 



The other two members of the group, Sargassurn asymmetricum and 

 S. MacDougalii, are distinguished from the foregoing by a branching 

 habit in which the primaiy branches are percurrent and the secondary 

 branches distinct, by the vesicles with prolonged, foliaceous extensions, 

 and by the large upper leaves, more than 1.5 cm. long. Reproductive ma- 

 terial is present only in S. asymmetricum, specimens of which were col- 

 lected in January at Turner's Island and at Puerto Refugio. The charac- 

 ters of the antheridial receptacles of this species are very much in accord 

 with those of S. lapazeanum, having the same branching structure and 

 denticulations. The vesicles are, however, very different in the occurrence 



