THE PLANT AND ITS FOOD 13 



CHAPTER II 



THE PLANT AND ITS FOOD 



ONE of the most striking points of difference 

 between the animals and the plants consists 

 in the evident and purposive motility of the 

 former, and the apparent (but only apparent) 

 immobility of the latter. Nearly all animals 

 more or less actively seek their food, and 

 ingest it in a solid form; and even those 

 species which, like the adult oyster, are 

 tolerably stationary, nevertheless exhibit some 

 sort of motion by which currents of water, 

 bearing particles of food are drawn into their 

 bodies. 



The general tendency in the plant kingdom, 

 on the other hand, has been to produce 

 relatively stationary forms which do not 

 actively pursue their food, but passively 

 absorb it from their surroundings. Many of 

 the most primitive plants, however, share 

 with the animals a faculty of vigorous loco- 

 motory movement, swimming through the 

 water in which they live by means of vibratile 

 filaments or cilia. What is it, then, which 

 has caused the higher members of the one 

 kingdom to abandon this locomotory activ- 

 ity while those of the other have not only 



