II] 



THE BEACH AND ROCKS 



17 



simple outline and full green colour, and it is fixed 

 bv a narrow stalk which widens into a minute 



*j 



attachment disc. The whole plant is very soft and 



- A 



Fig. 1. Ulva lactuca. 1. A complete specimen of the plant. 

 3. A longitudinal section from the upper part of the flat ex- 

 pansion, showing the two layers of cells of which it is composed. 

 2. A similar section from the lower part, showing similarly the 

 two layers of cells ; several of the latter have elongated into 

 tubes or hyphae (h). 2 and 3 are highly magnified. (From 

 0\tma,nns'~~Morphologie und Biologic der Algen, after Thuret.) 



B. 2 



