50 



PLANT LIFE 



degree of cellular differentiation is really not 

 essential for water plants, and we shall find 

 that the complex structure of terrestrial 

 species becomes simplified in any descendants 

 that may have taken to a watery habitat. 



Even amongst the algae high differentiation 

 of external form is not necessarily associated 



IJTT 



Fig. 7.Caulerpa StaUii. 



with a cellular complexity of corresponding 

 magnitude. This is well seen in those sea- 

 weeds that consist of a large number of cells 

 which, though enclosed in a common peri- 

 pheral membrane of cellulose, are not parti- 

 tioned off from each other by cell walls. An 

 example of such a plant, which combines 

 a somewhat highly differentiated external 

 form with an internal structure of remarkable 



