1925] Setchell-Gardner: Melmwphyceae 551 



solid when young, becoming more or less fistulose when old ; color dark 

 olive brown ; erect fronds annual, base perennial ; zoosporangia ellip- 

 soidal to obovoid, numerous, sessile on the parenchymatous cells or at 

 times lateral near the base of the paraphyses, 50-60/^ long, 30-40ju 

 broad, paraphyses numerous, clavate, 70-85/a long, terminal cell much 

 enlarged, pyriform to spherical; gametangia very compact, covering 

 the whole surface of the ramuli, without paraphyses or hairs, pluri- 

 seriate, terminating in a 2-3-celled, sterile, usually clavate tip ; plants 

 dioecious. 



Common on rocks in the middle and lower littoral belts. Ranging 

 from St. LawTence Island in the Bering Sea to central California 

 (near Point Conception). 



Setchell and Gardner, Phyc. Cont., VIT, 1924, p. 6. CJiordaria 

 abietina Ruprecht, MS. in FarloAv, List Mar. Alg. U. S., 1876, p. 357 ; 

 J. Agardh, Till Alg. Syst., part 2, 1882, p. 74, pi. 3, figs. 2a, 2h; 

 Saunders, Alg. Harriman Exp., 1901, p. 424 ; Setchell and Gardner, 

 Alg. N.W. Amer., 1903, p. 251, pi. 18, figs. 16, 17; Collins, Holden 

 and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 281; Tilden, Amer. Alg. 

 (Exsicc), no. 348; Farlow, Anderson and Eaton, Alg. Exsicc. Amer.- 

 Bor., no. 94. 



Heterochordaria ahietina (Rupr.) S. and G. is one of the very fre- 

 quently occurring algae of western North America from Point Con- 

 ception in California northwards. It has two striking peculiarities, 

 viz., the possession of a well developed horizontal thallus from which 

 the erect fronds arise and also of the gametophyte of the same size as 

 the sporophyte. The horizontal thallus is often a fair sized and 

 reasonably conspicuous structure, at times several centimeters in 

 diameter, spreading at the periphery and consisting of overlapping 

 narrow, blunt and emarginate lobes. Prom certain appearances, it 

 seems possible that it may be perennial. In the sporophyte, the zoo- 

 sporangia seem to be confined to the ramuli, and this seems to be the 

 case also with the gametangia of the gametophyte which have not been 

 seen to occur on the main axis. J. G. Agardh (1882, p. 74, pi. 3, figs. 

 2a, 2h) has figured and described the gametangia and Okamura (1910, 

 p. 122, pi. 85, figs. 14, 15) has figured and described both the zoo- 

 sporangia and the gametangia. We have previously (1903, pp. 251, 

 252, pi. 18, figs. 16, 17) figured and described the horizontal thallus. 



