THE ALGAE 



101 



Cladophora 



Species of this genus occur characteristically both in fresh water and also 

 in the sea, and a few species are epiphytic or even epizoic. The species are 

 very numerous and difficult to separate (Fig. 83). 



Fig. 83. — Cladophora rupestris. Form of entire plant. 



The thallus is composed of branched 

 cylindrical coenocytes joined end to 

 end. It is attached to the substratum 

 by means of branched, septate rhizoids. 

 Each branch grows by means of an 

 apical segment. The separate coeno- 

 cytes (Fig. 84) contain numerous 

 nuclei which are either embedded in 

 the meshes of the chloroplast or lie 

 internal to it. The structure of the 

 chloroplast is complex, and divergent 

 views exist regarding its nature. It 

 appears to consist of a parietal reticulum 

 which lies in the cytoplasm, though 

 additional chloroplast segments may 

 develop inwards into the central vacu- 

 ole. The meshes of this reticulum 

 cover the longitudinal and transverse 

 walls of the coenocyte and var\' much 

 in width. There are numerous pyre- 

 noids scattered in it which can 

 multiply by division. In unfavourable 

 conditions the chlorophyll may contract 



septate filaments formed of 



<2- ■ 





Wh4 



m. 





NUCLEI 



• CHLOROPLAST 



^ 



^(^;^-^(?t^^ PYRENOIDS 



Fig. 84. — Cladophora glomerata. Young 

 coenocyte in the autumn condition, 

 the pyrenoids containing starch. 

 {After Garter.) 



