HOW TO KNOW THE SEAWEEDS 



185a Rhizoidal filaments usually aggregated in the central part of the 



medulla; cystocarps with only one ostiole. Figs. 231, 232 



Pterocladia 



Figure 231 



Fig. 231. Pterocladia caloglossoides (Howe) Dawson 



A small portion of a branch showing two uniostiolate cystocarps, 

 X 16. In Gelidium, an ostiole appears on both bulging sides of the 

 cystocarp. 



Figure 232 



Fig. 232. Pterocladia pyramidale 

 (Gardner) Dawson 



A very small apical portion of 

 an axis to show the pinnate 

 branching and more or less pyra- 

 midal form, X 2.5. This is a com- 

 mon, intertidal plant of southern 

 California, often being a dominant 

 rock-cover alga. It is seasonally 

 variable in form, and old indi- 

 viduals often show much attenu- 

 ation of the ultimate branches 

 which become dense and some- 

 what matted. Other species of this 

 genus occur along the California 

 coast, but are small (P. caloglos- 

 soides) or scarce and local. 



175 



