THE PLANT AND THE ANIMAL 271 



Let us leave these conjectures for the present ^ and 

 study another question : Are we entitled to consider 

 the movements of plants described above as similar to 

 those in animals, or can some essential difference be 

 established between these two categories of phenomena ? 

 So far as the movement of protoplasm is concerned, it 

 does not present any difference whatever in the two 

 kingdoms. The same may be said of the movements 

 of the zoospores and antherozoids : here also no 

 difference can be established between the movements of 

 vegetable and animal organisms, which is proved by the 

 fact that the earliest investigators refused to believe 

 their own eyes and mistook for animals the motile 

 organs of plants. 



The case is rather different when we compare the 

 movements of the higher plants with those of animals. 

 At all events we do not find in the plant any special 

 tissue adapted for movement, any muscular fibre 

 capable of contraction. Yet we can hardly base upon 

 this difference in structure a fundamental difference be- 

 tween the phenomena. A comparison of the conditions 

 which determine and accompany the movements of the 

 higher plants and animals points rather to similarity 

 than difference between them. We know, for instance, 

 that motion in animals is closely bound up with respira- 

 tion : the contracting muscle absorbs more oxygen, gives 

 off more carbonic acid than a resting muscle, and 

 it is this oxidising process that serves as the main 

 source of the energy used in muscular activity. Now, 

 does the plant present phenomena similar to the 

 respiration of animals ? We have already met with 

 cases which prove this in the affirmative. During the 

 germination of seeds, the development of buds, especially 

 during the flowering period, these vegetable organs 

 greedily absorb oxygen and give off carbonic acid, 



^ All these explanations brought forward as conjectures (in 1876) have been 

 proved by subsequent investigators and adopted by almost all botanists. 



