NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 313 



tusis, omnibus acute inclinatis, e termino superno cellularum sustinentium orienti- 

 bus; tetrasporangiis in lateribus adaxialibus ramellorum ultimorum seriatis, ovoid- 

 eis, 45-55 |x diam. ; cystocarpiis circa 150 n diam., plerumque ramum secondarium 

 terminantibus. 



Plants tufted, epiphytic, to 2.5 cm. high, distichously branched, with 

 a central, uncorticated axis and frequent primary branches ; primary axis 

 about 150 fi diam. (of cylindrical cells slightly longer than thick) with 

 4 orders of branches gradually attenuated upward, but apices rather 

 blunt; cells in main axis slightly longer than broad; cells in ultimate 

 ramuli about twice as long as broad (cells in sterile portions usually 

 longer than those in fertile portions) ; all branches sharply inclined, com- 

 ing off at upper end of cells bearing them ; sporangia seriate on adaxial 

 sides of ultimate branches, arising at the top of each cell as a little peg, 

 enlarging to an ovate body; mature tetrasporangia measuring 45-55 fi, 

 tripartite; cystocarps occasional, usually terminal on a secondary branch, 

 about 150 /x diam. at maturity; antheridia in tufts along the adaxial side 

 of the 3-4 cells just above axil of ultimate branches. 



Type: D. 195, on shore, lower littoral, Puerto Refugio, Jan. 27, 

 1940 (tetrasporic). Herb. AHF no. 53. 



D. 381f, dredged in 22 meters, Tepoca Bay, Feb. 4, 1940 (antheridial 

 and cystocarpic). 



There are no distichous Callithamnion species described from the 

 North Pacific which exhibit the characters of our plants. The good for- 

 tune of having all reproductive stages gives us ample means of identifying 

 them, though the vegetative characters are also distinctive. 



Genus ANTITHAMNION Naegeli 

 Antithamnion sublittorale S. & G. 



Setch. & Card., 1937, p. 86, pi. 6, fig. 15. 



H. 613, 646a, 721, epiphytic on other algae dredged in 40 meters off 

 San Jose del Cabo, Aug. 



Antithamnion pacificum (Harv.) Kylin 



Kylin, 1925, p. 47, fig. 29. 



D. 381e from 22 meters at Tepoca Bay, February, is indistinguishable 

 from Kylin's illustrations (loc. cit.), and the specimens agree with his 

 key characters for this species described from Puget Sound. 



A specimen from 30-36 meters in Ensenada de San Francisco, near 

 Guaymas, February, is evidently the same but has shorter branchlets due 

 to their shorter cells. 



