CLADOPHORA 427 



and development of the zygospore, since it undergoes 

 a period of rest during the summer months, and 

 its progress is very slow during the succeeding 

 winter. 



Preparations showing active zoospores should be 

 treated with iodine solution, by which they will be 

 killed, and the observation of the cilia will be easy 

 by reason of the staining : note the four cilia in the 

 macro-zoospores, while there are only two in those 

 micro-zoospores which have not conjugated. 



Trace the processes of change in the cells of the filament pre- 

 ceding the escape of the zoospores : according to Dodel and others 

 their formation is hy a process of cell-division : Strasburger, 

 however, states that the process is simultaneous ; being a case of 

 free cell-formation, preceded, however, by a process of nuclear 

 division. 



CLADOPHORA 



Various species of Cladophora are to be found inhabiting fresh 

 or salt water : perhaps the commonest, and the most easily 

 recognized, is Cladophora rupestris, which grows at all levels 

 between the tide marks on rocky coasts. Its coarse and rigid 

 filaments are of a deep green colour, and are profusely branched, 

 so that the plants as a whole appear as dark green tufts, easily recog- 

 nized after being once seen. The plant may be examined fresh, 

 and be mounted in sea water ; or, if necessary, material preserved 

 in weak alcohol may be used. 



Having mounted a small piece of the plant, examine it under 

 a low power, and note 



1. The irregular cylindrical form of the filaments, which 

 are divided by transverse septa into cells of consider- 

 able length : they are profusely branched, and two 

 or three branches may be inserted at one point, the 

 insertion being lateral and just below a septum. 



