HOW TO KNOW THE SEAWEEDS 



83b Thallus brown 84 



84a Thallus slippery, structurally composed of branched filaments. 

 Fig. 119 Leathesia 



Fig. 119. Leathesia difformis (Linnaeus) 

 Areschoug 



A small portion of the outer tissues of a 

 plant to show the filamentous structure 

 which includes vegetative filaments, para- 

 physes, gametangia and a hair, X 240. 

 This is a common, small, subspherical plant 

 on rocks and algae, especially on Coral- 

 lina. It occurs along the entire Pacific 

 Coast and in the cooler Atlantic waters 

 north of North Carolina. Only one other 

 local California species of the genus grows 

 within our area. 



Figure 119 



84b Thallus not slippery, crisp, structurally composed of parenchymat- 

 ous cells. Fig. 120 Colpoznenia sinuosa 



Fig. 120. Colpomenia sinuosa 

 (Roth) Derbes & SoUer 



Habit of a subspherical plant, 

 X 1.5. This plant may be en- 

 countered in Florida and in the 

 summer along most any part of 

 the Pacific Coast especially in 

 waters subject to marked warm- 

 ing. It is exceedingly variable, 

 from small, spherical epiphytic 

 plants to large, broad, prostrate 

 or floating ones in which the hol- 

 low form has reached a state of 

 collapse. 



Figure 120 



91 



