NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 97 



sporangia are so unlike those of the common H. prototypus that the 

 present plants may be worthy of specific rank. Our specimens differ 

 from H. canariensis B^rgesen in the presence of paraphyses as in typical 

 H. prototypus. The tetrasporangia are transversely divided unlike the 

 obliquely divided ones of H. crouani (J. Ag.) J. Ag. There seems to be 

 little difference from H. yezzoensis Yendo of Japan, but suitable com- 

 parative material of this more recently described and possibly synony- 

 mous plant is not available to the writer. 



The plants in both cases were found growing in the vicinity of 

 typical H. prototypus and could be distinguished from them macro- 

 scopically by the duller reddish color. For these reasons one is led to 

 suppose that the two may prove to be specifically distinct, although re- 

 investigation of the poorly known van kerguelensis in the type locality 

 should be carried out before a decision is reached. Indeed, the Mexican 

 specimens may prove to be different from the Kerguelen Islands plant 

 when the latter becomes better known. 



Squamariaceae 



Key TO THE Mexican Genera and Species 



1. Tetrasporangia zonate .... Haematocelis rubens 



1. Tetrasporangia cruciate 2 



2. Tetrasporangia borne terminally on a 2-6-celled filament 

 among similar sterile filaments not in special nemathecial 



sori Cruoriopsis mexicana 



2. Tetrasporangia sessile or on a 1 -celled pedicel among para- 

 phrases in a special nemathecial sorus 3 



3. Thallus with ascending and descending perithallus cell-rows 



from a mesothallus layer .... Ethelia mexicana 



3. Thallus with vertical or ascending perithallus cell-rows arising 



from a unistratose hypothallus 4 



4. Hypothallus as seen from below of more or less uniform 



parallel cell-rows Peyssonelia 5 



4. Hypothallus as seen from below of many small fan-shaped 

 groups of cells converging and diverging irregularly 



Cruoriella 12 



5. Thallus subfoliaceous, loosely attached by long multicellular 



rhizoids P. squamaria 



5. Thallus crustose, more or less closely attached by relatively 

 short, uni-multicellular rhizoids 6 



