NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 107 



vertical rows of rectangular cells mostly twice as long as broad, these 

 rows once or twice branched in the 2nd-3rd or to the 5th tier, the cells 

 decreasing in size and in relative height toward the superior surface 

 where the uppermost ones are shorter than broad and only 6-8 /a in 

 greatest diameter; tetrasporangial nemathecia elevated above surface of 

 surrounding vegetative tissue, 130-150 /a thick, of rather dense, slender, 

 unbranched paraphyses as little as 2 ft wide at the base, 5 /a at the top, 

 of about 7 elongated cells, the upper 2-3 shorter, the terminal one often 

 more or less pointed; tetrasporangia narrow, especially when young, 

 maturing 60-100 fi long, 22-30 (35) /* broad; sexual reproduction not 

 observed. 



Type: Holotype is Dawson 3867, Feb. 2, 1947, in vial 2346 and 

 on slides 1856-1858 in HAHF. 



Type locality: On granitic outcrops, southeast side of Bahia 

 Acapulco, Guerrero, Mexico. 



Additional material: D. 3927, outer wave dashed rocks on reef 

 near Playa Angosta, Acapulco, Guerrero, Feb.; D. 117, Cabo Colnett, 

 Baja Calif., Jan. 



This species superficially resembles Peyssonelia pacifica, but differs 

 in several points of structure and in the elevation of the nemathecia. It 

 is distinct from other peyssoneliae by manner of its thick thallus, ascend- 

 ing perithallus cell rows, unicellular rhizoids, and superficial nemathecia 

 with slender, unbranched paraphyses which are usually considerably 

 smaller at their bases than the vegetative cells from which they arise. 



The Cabo Colnett collection, although apparently representative of 

 quite a different temperature province from that of the type, differs 

 only in its lesser calcification and slightly larger cells throughout. 



Peyssonelia calcea Heydrich 



Heydrich, 1897, p. 10; Weber van Bosse, 1921, p. 277, fig. 94; 

 Taylor, 1945, p. 169. 



Thallus crustose, forming irregular" discs more than 5 cm. in dia- 

 meter, the margin lobed, the surface dull, brownish or yellowish when 

 dry with darker glutinous spots, moderately closely adherent without 

 any free lobes but readily cracking off the rocky substratum when dry, 

 the lower portion firmly calcified, only the uppermost, small-celled por- 

 tions of the perithallus free from lime, to 450 /x thick; hypothallus of 

 one layer of cells mostly 45-55 ix high, 45-80 yu, long, provided on the 

 under side with a pronounced cuticle 8-16 /* thick and with many short, 



