25 



volume to the amount of CO^ decomposed. This 

 process is called Assimilation, and may be repre- 

 sented thus:— 6 CO2 + 5 H2O = Ce Hio O5 -f 6 O^. 

 The Chlorophyll grains are larger than the ordin- 

 ary grains of protoplasm, and as a rule lie next to 

 the cell wall. The nucleus occupies the centre. 



'I he changes to the active condition are as follows : — 



(1) The protoplasm withdraws itself from the 

 wall, except at two points. 



(2) The protoplasm at these points protrudes 

 through the wall as long threads. 



(3) The cell wall becomes disorganised, and it now 

 swims about as a naked cell, called a Zoospore, 

 in which a red spot is clearly visible. This is 

 known as the ** Eye-spot." 



Note. — One cell may produce as many as eight 

 zoospores, thus : 



(1) The protoplasm splits into as many parts as 

 there are zoospores to be formed. 



(2) Each mass develops two cilia, which protrude 

 through the wall. 



(3) The mother cell is disorganised, and the 

 zoospores are liberated. 



Changes to the encysted condition. 



(1) It loses its cilia. 



(2) It clothes itself with a cell wall, and becomes 

 quiescent. 



