82 PLANT-LIFE ON LAND [CH. 



plants seen in the growing state the fixity of position 

 which is so prevalent a factor in plant-life. 



It was long ago laid down as a general distinction 

 between animals and plants, that plants live, while 

 animals live and move. This antithesis still survives 

 in the mouth of the artist when he includes plants 

 under his designation of "still life." It is hardly 

 necessary to-day to refute this distinction, or to show 

 how far it is from accordance with fact. Every 

 elementary student knows that active life and move- 

 ment in some degree are inseparable. The movement 

 may be molecular only, or intracellular : in either case 

 it would be invisible to the naked eye, but still it 

 would be there. Moreover, the student soon learns 

 how closely such movements depend for their activity 

 upon those conditions which favour vigorous physio- 

 logical change : for him movement of some sort is 

 a common expression of life in plants as well as in 

 animals. Darwin's well-known book on the Power 

 of Movement in Plants has gone far to disillusion the 

 public on the point. He there showed that, apart 

 from the more rapid and obvious movements in such 

 cases as the sensitive plant (Mimosa}, ordinary seed- 

 lings and growing plants at large execute movements. 

 These, being slow, are for the most part indistinguish- 

 able by the naked eye, but they may be readily 

 demonstrated by simple means. Thus we approach 

 the conclusion that even plants move in greater or 



