APPENDIX 351 



formation of organic matter in a plant is accompanied by the 

 absorption of as much heat as is liberated in burning it down. 

 Thus, for instance, if a plant liberates i.ooo units of heat when 

 it burns, we may conclude that at least a similar amount of the 

 heat of the sun has been used up in its growth ; and however 

 we may manure our soil and cultivate our land, if the sun does 

 not provide it with these i.ooo units of heat we shall not 

 get our plant. 



Thus it is that, knowing on the one hand the amount of 

 combustible matter (to be ascertained by analysis) contained 

 in a crop obtained from a certain area of land, and knowing on 

 the other hand the amount of heat cast by the sun upon this 

 area., we have all the necessary data for calculating the profit 

 and loss of the energy of the sun in our field, and hence to 

 decide what proportion of it we use and what there is yet to 

 be used. Such calculations for the crops which yield the largest 

 amount of organic matter, the richest harvest, bring us to the 

 following conclusions. The largest annual increase of matter in 

 woods represents something like ^^ih of all the amount of heat 

 received by the area of land which they occupy during the 

 period of growth. The increase in bulk of the roots is not 

 taken into this calculation. The Jerusalem artichoke, one of 

 the plants which undergoes the most intensive cultivation, uses 

 in this way T |Q th of all the energy it receives from the sun. The 

 organic matter in the richest crop of hay (rye grass) , including the 

 root remains, stores up T J-th of the energy of the sunlight. Lastly, 

 the best crops of oats and rye (grain, straw, and root remains) 

 represent ^th of all the energy they receive from the sun. Thus 

 by means of a plant we are able to avail ourselves approximately 

 of a quantity varying from T ^y ^th to yj^th of the total amount of 

 sunlight which falls upon the surface of our forests and fields during 

 the growing period. 1 Are we therefore entitled to say that by 

 improving our methods of culture we shall be able to increase 

 the crops by one hundred if not by one thousand times before we 

 reach the limit of productiveness ? Is the plant able to store 

 up all the energy it receives from the sun ? Certainly not. 

 We know that no mechanism or organism makes exception to 



1 It is clear that these numbers are not very strict. The number 

 quoted for the amount of heat that falls upon a given area, taken from 

 Pouillet's data, is only approximately true. 



