EUPHYCOPHYTA 89 



cytic wall enclosing a fluid, but this interpretation leads to diffi- 

 culties. In some respects, therefore, the genus provides a link with 

 the Siphonales. The macroscopic club-shaped vesicle is attached 

 to the substrate by rhizoids of various types. There is a lobed 

 chloroplast that congregates with the cytoplasm at certain points in 

 the older plants and then each group is cut off by a membrane, thus 



Fig. 48 Cladophoropsis memhranacea. a, part of plant showing 

 characteristic branching; b-d, stages in segregative cell division, 

 wall formation and start of branching (b-d, after Borgesen) (all 



X15). 



producing a number of marginal cells. This type of division in 

 which groups of cytoplasm are formed in the parent cell and then 

 surrounded by new membranes is known as segregative cell divi- 

 sion. The cells do not necessarily form a continuous layer and are 

 frequently restricted to the basal region where they may develop 

 rhizoids, whilst in other species they are nearer to the apex where 

 they may give rise to proliferations. The lower cells can form short 

 creeping branches, and as these bear more of the erect vesicles a 

 tuft of plants is produced. 



Reproduction takes place by means of bi- or quadriflagellate 

 swarmers, which are Hberated from the cells through several pores, 



