286 THE LIFE OF THE PLANT 



energy stored by plants ; plants in their turn derive the 

 energy they require from the sun. Animals depend on 

 plants and plants depend on the sun. 



We arrive in this way at the most general conception 

 of the life of the plant, at the realisation of its principal 

 function, the part it plays in the organic world. It plays 

 the part of mediator between the sun and the animal 

 world. The plant — or rather, its most typical organ, 

 the chloroplast — is the link which unites the activity 

 of the whole organic world, all that we call life, to 

 the centre of energy in our solar system. Such is the 

 cosmical function of the plant. 



When the type of a green oak rises before our imagina- 

 tion, rustling its luxuriant foliage in summer, bare and 

 frozen in winter, enduring all the fluctuations of the 

 external temperature ; when we think of that oak year 

 after year, century after century increasing in organic 

 mass, yet always fixed to the same place, and then look 

 at a Russian trotter flying like an arrow, giving off in 

 winter clouds of vapour, and learn that it uses both in 

 winter and in summer quantities of hay and grain ; when 

 we subsequently learn that these opposite external 

 phenomena are only the necessary results of the chemical 

 processes which predominate in the one or the other case ; 

 then the antithesis between plants and animals stands out 

 clearly before us. But when we venture to cast a general 

 glance not only upon these typical representatives, but 

 upon all plants and animals and upon the whole of their 

 functions, we are compelled to realise the inadequacy 

 of such an antithesis. This contradiction vanishes, and 

 everything becomes comprehensible the moment we ad- 

 mit that the stream of organic life, working its course 

 in the beginning along a single bed, has subsequently 

 divided into two branches ; so that now, standing at 

 their mouth, we seem to see two independent currents. 

 It is only when we try to follow both currents along 

 their entire course till we rise to their common source 



