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 
