HOW TO KNOW THE SEAWEEDS 



187a Tetrasporangia borne in globose masses inside the cortex. Fig. 

 236 Gigartina (in part) 



Fig. 236. Gigartina canaliculaia 

 Harvey- 

 Part of a cystocarpic plant ex- 

 tracted from a clump, X O-^- This 

 is one of the commonest inter- 

 tidal algae along the CaHfomia 

 coast, extending northward into 

 Oregon. It is often a dominant 

 member of rock-cover associations. 



Another species which may best 

 key out here is the CaHfomian G. 

 leptorhynchos J. Agardh which is 

 of blackish color and provided 

 with abundant, small, slender, 

 spinose outgrowths on all sur- 

 faces. 



For comments and illustrations 

 of other forms of Gigartina see 

 steps 151a and 168a. 



I 



J 



Figure 236 



187b Tetrasporangia not borne in globose masses inside the cortex but 

 scattered and more or less solitary, or in nemathecia. Fig. 237. . 188 



Fig. 237. Grateloupia sp. 



One of the soHtary. scattered tetrasporangia 

 as found in this genus in contrast to the glo- 

 bose masses occurring in Gigartina. 



Figure 237 



178 



