HOW TO KNOW THE SEAWEEDS 



186a Medulla entirely composed of parenchyma type cells. Fig. 234. . . 

 GracilaTia foJii/era 



Fig. 234. Gracilaria toliifera 

 (Forskal) Borgesen 



An entire small plant 

 showing the irregular 

 branching in one plane, 

 X 0.64. This is a common 

 and exceedingly variable 

 plant ranging along the At- 

 lantic Coast from Florida to 

 Massachusetts in a variety 

 of habitats, often in quiet, 

 shallow water. It is our 

 only common and wide- 

 spread representative of a 

 varied assemblage of flat 

 species of Gracilaria, usu- 

 a 1 1 y of subdichotomous 

 branching. See step 23a 

 for comments on cylindri- 

 cal species of this genus. 



Figure 234 



186b Medulla composed of filamentous cells. Fig. 235 187 



Fig. 235. Grateloupia sp. 



A pojtion of a transection of a thallus 

 to show the structure of filamentous type 

 cells. The medullary cells are seen to be 

 slender, often branched filaments loose- 

 ly arranged in a jelly-like matrix. 



Figure 235 



177 



