350 THE LIFE OF THE PLANT 



food. On the strength of what has akeady been achieved by 

 synthetic chemistry, we can scarcely doubt that in the future, 

 it may be at no very distant date, science will reaUse these 

 expectations. At all events there is no such fundamental 

 difference between what has been already achieved and what 

 yet remains to be done as to make such a hope improbable. And 

 then if food actually becomes artificial, will not agriculture be a 

 thing of the past ? Will not land lose its value ? Will not the 

 economic order of things entirely change ? Let us see how far 

 these conjectures are true. We saw that to form an organic 

 body energy is required. On burning down a pound of bread 

 eight hundred and ninety units of heat are produced. Therefore, 

 to form it either naturally or artificially, a similar amount of heat 

 must be used, or speaking more generally a similar amount of 

 energy. Whence is this energy to be obtained ? The only source 

 of energy free of cost is the sun. Therefore, in order to produce 

 artificial food our remote posterity wiU have to imitate plants 

 by covering the surface of the earth with artificial absorbers 

 of sunlight. Such imitation cannot be said to be an easy matter, 

 because from this point of view the plant presents a very perfect 

 apparatus. A glance at the thickness of the grass in any meadow 

 is enough to convince us of the fact that every bit of soil is at 

 present utilised. Calculations furnish us with data still more 

 eloquent. Thus, for instance, the total surface of the leaves of 

 a clover plant exceeds twenty-six times the area of the land 

 occupied by the plant, so that an acre of clover is equal to 

 twenty-six acres of green surface absorbing the rays of the sun. 

 Other plants occupy even larger surfaces still. The sainfoin 

 has a leaf-surface thirty-eight and lucerne eighty-five times 

 larger than the areas they occupy. Mixed grasses would 

 probably give stiU higher numbers. 



Here another curious theoretical problem occurs to us: Can 

 we indefinitely increase by means of plants the amount of 

 organic matter obtainable from a certain area of land ? Can 

 we expect that by means of improvements we shall indefinitely 

 increase the productiveness of our soil, or has it a limit ? This 

 is the problem of the future fate of humanity. The data we 

 already possess permit us to decide this question in the affirma- 

 tive. There is a limit, and we are even able to determine it 

 approximately. We have already said many times that the 



