THE PLANT AND THE ANIMAL 287 



that we come to the conclusion that they are only two 

 branches of one and the same potent stream of life. 



With this we sum up the survey of the vital functions 

 of the plant. We have studied the structure of its 

 different organs, have learnt their significance, and have 

 thus solved a twofold problem, which is always facing 

 the physiologist : given an organ, to find its function ; 

 given a function, to find an organ corresponding to it. 

 We have observed how perfectly every single organ 

 fulfils its function, how well it is adapted to its environ- 

 ment, how indispensable is the reciprocal activity of 

 different organs, and how harmoniously they work 

 together in the general life of the plant ; how remarkable 

 is the co-operation of certain organisms, though belong- 

 ing to different kingdoms of the organic world ; how 

 harmonious is the reciprocal activity of these two 

 kingdoms taken together. The study of all these facts 

 seems to justify us in saying we have reached the end of 

 our course. But it is precisely here, at this apparent 

 limit, that the physiologist begins to realise, though 

 faintly, that his subject is not exhausted, that beyond all 

 these particular problems there arises the most general 

 and universal inquiry : Why is it that all these organs, 

 all these beings are so perfect, so wonderfully adapted 

 to their environment and functions ? The more striking 

 the fact, the more perfect the organism, the more 

 haunting is the question : Why is it so perfect ? By 

 what means has it reached this perfection ? Is it 

 worth while to go through such a long course in order 

 to hear at the end the laconic answer : I do not* know, 

 nor understand, nor shall ever understand. It is true 

 that a naturalist is liable to say this, is even more 

 liable with sincerity to give this answer than any 

 other investigator ; but, at the same time, he most 

 willingly grasps the first opportunity for an explanation, 



