HOW TO KNOW THE SEAWEEDS 



111b Base of plant solid, calcified, without penetrating filaments. (See 

 remark under Fig. 148) 112 



112a Segments more than twice as broad as thick. Fig. 148 113 



Figure 148 



Fig. 148. Bossea sp. 



A small upper part of a plant to show the broad, winged inter- 

 genicula more than twice as broad as thick. Close inspection of a 

 plant of Bossea, or of one of the other articulated coralline genera 

 treated below through step 116, will show that as it grows intact on 

 its rock, or in the case of Jania, its host plant, it consists of two parts. 

 The erect, jointed parts are conspicuous, but there is also a thin, 

 crustose film spreading over the rock and adhering completely to it. 

 This basal crust cannot usually be removed with the specimen unless 

 a piece of the rock is taken. 



112b Segments cylindrical to compressed, mostly less than twice as 

 broad as thick IM 



114 



