HOW TO KNOW THE SEAWEEDS 



185b Rhizoidal filaments usually aggregated in the outer portion of the 



medulla; cystocarps with two ostioles. Fig. 233 



Gelidium (in part) 



Figure 233 



Fig. 233. Gelidium puipuiacens Gardner 



A small portion of a tetrasporangial plant, X 8. This is only one 

 of several similar, moderate to large species of Gelidium inhabiting 

 rocky intertidal and infratidal areas along the Pacific Coast. They ore 

 usually strongly compressed in shape, but not very flat. (See also 

 step 45a) G. carfiiagineum variety robustum Gardner, which occurs 

 along the entire coast, but especially in California, is the largest and 

 most abundant. It has been harvested by diver in southern Cah- 

 fornia for the making of agar, especially during World War II when 

 the demand for domestic agar weeds was great and the Japanese 

 supply cut off. Currently, the high cost of harvesting by professional 

 diver in the United States has favored the importation of raw Gelidium 

 weed from Japan and from nearby Baja California, Mexico along whose 

 cool shores it grows profusely. 



Among the other species of Gelidium which may be recognized 

 along the Pacific Coast are the polystichously branched G. poiysfichum 

 from the southern California Channel Islands, and G. papeniussii from 

 southern California which is distichous and distinguished by tetraspor- 

 angial branchlets with long, slender "stipes." G. pulchrum from south- 

 ern California is a rather delicate species with tetrasporangia borne 

 in short, clavate ultimate branchlets. 



176 



