THE PLANT IN ACTION. 259 



place by what are called " zoospores," and which are 

 represented in Fig. 414. It appears, from the latest ex- 

 aminations, that these zoospores, which are of extreme 

 minuteness, are of ovoid shape, and are partially or 

 wholly covered with those extremely fine, hair-like 



FIG. 414. 



bodies, known as cilia, which have the power of 

 spontaneously vibrating, or lashing backward and 

 forward. They exist upon the surface of animal 

 membranes, and, by their rapid, incessant, whipping 

 motion, they cause the agitation and circulation of 

 fluids upon such surfaces. Now, as soon as these 

 minute zoospores free themselves from the parent- 

 cell, the cilia begin to vibrate with great rapidity, 

 the vibrations being accompanied by a movement of 

 rotation of the cell, and the result is a quick motion 

 of the body through the water, similar to the move- 

 ments of the lower forms of animal life. After the 

 motion has continued from half an hour to several 

 hours, the zoospores settle down, lose their cilia, and 

 give rise, by cell-division, to new organisms, resem- 

 bling the parent. (Some algae have a peculiar undu- 

 latory motion, hence they are called oscillatoria.) 



In the case of higher plants, there are many capa- 

 ble of peculiar motions, some of which seem to re- 



