240 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



(pi. 32). There are frequent instances elsewhere, as will be shown later, 

 in which this feature is very obvious. It often causes considerable differ- 

 ence in appearance of the fruiting parts of the two sexes. In two collec- 

 tions we have plants of both sexes from the same locality, and it is thus 

 possible to make some statement regarding sexual variation. The plant 

 called Sargassum Johnstonii f. laxius, for instance, is an antheridial plant 

 from the same collection as that named S. Johnstonii f. gracile, an oogo- 

 nial plant. 



The species Sargassum guardiense was distinguished principally be- 

 cause of its heteroclyte cyme and short apiculae. The type plant is oogo- 

 nial, and vesicles, as might be expected from the foregoing, are to be found 

 associated closely with the receptacles in the inflorescences. The observa- 

 tions that these often emerge from receptacular tissue gave rise to the 

 idea that this plant was distinct from S. Johnstonii. D. 476, however, is a 

 collection including both sexes, the oogonial plant of which is identical in 

 this respect with the type of S. guardiense. The antheridial plant shows no 

 such emergence of vesicles from receptacular tissue, and, furthermore, the 

 vesicles are not so important an element of the inflorescence as are the 

 leaves, evidence again of the above-mentioned idea of the inflorescence 

 associations. This heteroclyte cyme character is, then, clearly one of sexual 

 variation in these plants and cannot be relied upon to separate species. 

 Sargassum guardiense S. & G. thus falls in as synonymous with S. John- 

 stonii, and we have only the one species and its variety as constituting this 

 first group. 



Sargassum Johnstonii S. & G. 



Plate 32, Figs. 1-15; Plate 33, Figs. 1, 2, 17-22 



Setch. & Gard., 1924, p. 737, pi. 20, fig. 72, pi. 21, fig. 80. Sargassum 

 guardiense Setch. & Gard., 1924, p. 732, pi. 19, fig. 64. 

 Basal parts unknown; plants long and stringy, 1-2 m., with terete, 

 smooth primary axes usually continuous from the base ; secondary branch- 

 ing bifarious, at intervals of 3-10 cm., alternate and open below, more 

 closely spaced and sometimes almost opposite above, the branches of more 

 or less equal length, forming a fairly symmetrical branch system densely 

 crowded with fructiferous ramuli; leaves narrowly lanceolate to linear, 

 1.25-2.25 cm. long, 1-2.5 mm. wide, expanded, ecostate or rarely dimly 

 costate, with sparsely denticulate margins; cryptostomata not abundant 

 but fairly conspicuous ; vesicles smooth, narrowly elliptical, 5-9 mm. over- 

 all, merging below gradually into a pedicel somewhat shorter than the 



