1925] Setchell-Gardner: Melanophyceae 653 



except along the thickened margins of the old fronds where it is 

 double ; cortex of a single layer of colored cells, except in older, thick- 

 ened margins where there are two layers, arranged in longitudinal 

 parallel series ; oogonia, antheridia, and tetrasporangia all growing on 

 different individuals ; oogonia scattered in small sori ; antheridia and 

 tetrasporangia in oval or oblong sori ; reproductive cells on both 

 surfaces of the frond. 



Growing on boulders in the lower littoral belt. Southern Cali- 

 fornia. 



Setchell and Gardner, Phyc. Cont. VII, 1924, p. 12. Dilophus 

 flahellatus Collins, in Collins, Holden and Setchell, Phyc. Bor.-Amer. 

 (Exsicc), no. 834. Glossoplwra Kunthii Tilden, Amer. Alg. (Exsicc), 

 no. 334. Dictyota dichotoma Tilden, Amer. Alg., no. 335 (not Lamour.). 



This seems to be a distinct species, thus far confined to southern 

 California, but with unattached specimens collected at Monterey, Cali- 

 fornia, and Tracyton, Washington, probably sporadic or transported 

 to the latter. The species has the least doubling of the marginal cells 

 of any in our territory and is closely related to D. Binghamiae. It is 

 thinner, lighter colored, more pseudodichotomous, with the uppermost 

 almost pinnately arranged lobes short and bent. It is not difficult to 

 separate the two species when in company, either living or in her- 

 barium specimens, but we do find it difficult to express definitely the 

 exact points of distinction between them. 



3. Dictyota Johnstonii S. and G. 



Fronds 12-16 cm. high, 5-8 mm. wide, 125-135/x thick, composed 

 of a single layer of large medullary cells surrounded by a single sur- 

 face layer of small cells except in the lower part, along the margin the 

 medullary and surface cells becoming doubled, slightly stupose at the 

 base, pinnate, dichotomously branched, angles acute to somewhat 

 rounded, branches strict, margins smooth, color dark brown, black on 

 drying ; oogonia aggregated into elliptical or elongated areas, 115-125/a 

 long, 80-90/i, wide ; tetrasporangia and antheridia unknown. 



Growing on rocks in the upper sublittoral belt. San Marcos Island, 

 Gulf of California. 



Setchell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 730, pi. 18, 

 figs. 54-56, and plate 39. 



Dictyota Johnstonii appears to belong to the subgenus or section 

 of the genus, Strigocarpus J. Agardh (Anal. Algol. Cont. I, 1894, 



