330 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



Besides the specimens of Johnston, Brandegee, and Marchant cited 

 in the 1924 publication, recent material has been taken from both lower 

 littoral and sublittoral collections at Puerto Refugio, D. 236, 258, 284, 

 in January. D. 284 is an example having two tetrasporangia per segment. 



Polysiphonia Snyderae Kylin 



Kylin, 1941, p. 35, pi. 12, fig. 34. Polysiphonia senticulosa, Collins, 

 Holden & Setchell, Phyc. Bor. Amer. no. 638. 



This is the commonest species in the winter collections from the Gulf. 

 It is distinguished readily from other Gulf species except Polysiphonia 

 sonorensis by its slender proportions, its four pericentral cells, and its 

 elongated segments. It differs from P. sonorensis In color and habit. Kylin 

 has given a good habit figure and ample discussion of the plant's nature 

 and relationships. 



Examples have been found in the Gulf in various habitats and in all 

 parts of the region. It is particularly abundant and widespread in the 

 winter collections. 



Polysiphonia sonorensis Hollenberg 



Hollenberg, 1942, pp. 779-780, figs. 5, 20. 



Plants forming dense tufts of a terra cotta color, 4-5 cm. high, from 

 prostrate creeping filaments; prostrate filaments 120-175 fi diam., at- 

 tached by unicellular rhizoids which arise as outgrowths from the center 

 of the pericentral cells, from which they are not cut off by a cross wall ; 

 erect branches assurgent and arising exogenously, or mostly endogenously 

 from the prostrate branches, 70-100 fi diam., of segments mostly 1.5-2 

 diam. long; branching dense, the branches arising exogenously at irregu- 

 lar intervals (4) -10-20 or more segments apart, mostly at an acute angle 

 with the main axis, which is usually indistinct ; ultimate branches slender, 

 30-35 IX diam., slightly narrowed at the base, of segments mostly 1 diam. 

 long or shorter; pericentral cells 4, ecorticate; trichoblasts abundant, 

 arising at irregular intervals, once or twice forked, delicate, to 1 mm. 

 long, deciduous, often leaving inconspicuous scar-cells ; branches not asso- 

 ciated with trichoblasts in origin ; reproduction unknown ; plants ad- 

 hering moderately well to paper from which they are readily removed. 



Type: D. & R. 3426a, drifting along southeastern shore of bay, 

 Empalme, near Guaymas, Sonora, Dec. 23, 1939. 



