LINEAR AND SUPERFICIAL AGGREGATES. 25 



like branches, w, on the other. Not only are a base 



(posterior end) and an apex (anterior end) distinguishable, 



but the plant shows a difference between 



an upper (dorsal) and under (ventral) 



side, the leaf-like thallus lobes arisiiiL; 



from the dorsal side, while rhizoids 



spring from the ventral side. 



30. The thallus. — To the loose 



aggregation of single cells into colonies F.g. 33. - Transverse section 

 ^ - - , _ ,, of a-xis of Caulerpa^ show- 



ot dehnite lorm, as well as to the body ing cross-bars to stiffen wall. 



- , . . . . Maifnified about 25 diam. — 



lormed by their more intimate union Alter Murray. 

 in the linear and superficial aggregates just described, the 

 name thallus is applied. The term is most frequently applied 

 to those more complicated forms which constitute the vege- 

 tative bodies of the higher alga;, which are now to be 

 described. 



