FILAMENTOUS ALGjS. 



21 



axis, v-s, creeping in the mud, which bears green leaf-like 

 branches, b, on one side and, clusters of colorless root-like 



Fig. 21.— Part of a plant of Caulerpa. See text, 1 27. 

 After Sachs. 



Two-thirds natural size. — 



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 arising from 



the dorsal side, while rhizoids spring 



from the ventral side. 



28. The thallus.— To the loose ag- 

 gregation of single cells into colonies of 



, _ . Fig. 22. — Transverse section 



dennite form, as well as to the body of axis of Canierfa, show- 



. . . . . ing cross-bars to stiffen wall. 



formed by their more intimate union in Magnified about 25 diam.— 



. , ., , After Murray. 



the cell rows and masses just described, 

 the name thallus is applied. The term is most frequently 

 applied to those more complicated forms which constitute 

 the vegetative bodies of the higher algae, which are now 

 to be described. 



29. Summary. — Instead of being loesely associated in e©!- 



