xvi PLANTS IN RELATION TO MAN 329 



insect's transformations, does the agency of such a supreme 

 mind seem to be essential. 



Let us consider first the extreme simplicity and uniformity 

 of the conditions under which such marvellously diverse re- 

 sults are produced. A very large proportion of the vegetable 

 products useful to man are obtained from the tropical forests, 

 where the temperature is more uniform, the moisture more 

 constant, and the trees less exposed to wind than anywhere 

 else in the world. The whole organisation of the higher 

 plants is, as compared with that of animals, extremely simple, 

 and they are wonderfully similar in structure to each other, 

 even in distinct genera and natural orders. The roots, the 

 wood, the bark, the leaves, are substantially of the same type 

 in thousands of species. All alike build up their structures 

 out of the same elements, which they obtain from the water 

 and the few substances it dissolves out of the soil ; from the 

 air and the carbonic acid and aqueous vapour it contains. 

 Yet under these conditions what a seemingly impossible 

 variety of products arise. 



When the modern chemist attempts to bring about the 

 same results as are effected by nature in the plant, he has to 

 employ all the resources of his art. He has to apply great 

 heat or great cold ; he uses gas or electric fires and crucibles ; 

 he requires retorts for distillation, and air-tight vessels and 

 tubes for the action of his reagents, or to preserve his liquid 

 or gaseous products ; but with all his work, carried out for 

 more than a century by thousands of earnest students, he 

 has only been able to reproduce in his laboratory a limited 

 number of organic substances, while the more important of 

 the constituents of living organisms remain far beyond his 

 powers of synthesis. 



The conditions under which nature works in the vegetable 

 kingdom are the very opposite of all this. Starting from 

 the ripened seed, consisting essentially of a single fertilised 

 cell and a surrounding mass of nutritive material, a root is 

 sent out into the soil and a shoot into the atmosphere, from 

 which the whole plant with all its tissues and vessels are 

 formed, enabling it to rise up into the air so as to obtain 

 exposure to light, to lift up tons weight of material in the 

 form of limbs, branches, and foliage of forest trees, often to 



