182 DRY-FARMING 
spires excessively and the crops are consequently 
more subject to drouth. , 
The investigators of almost a generation ago also 
determined beyond question that whenever a com- 
plete nutrient solution is presented to plants, that is, 
a solution containing all the necessary plant-foods 
in the proper proportions, the transpiration is reduced 
immensely. It is not necessary that the plant-foods 
should be presented in a water solution in order to 
effect this reduction in transpiration; if they are 
added to the soil on which plants are growing, the 
same effect will result. The addition of commercial 
fertilizers to the soil will therefore diminish tran- 
spiration. It was further discovered nearly half a 
century ago that similar plants growing on different 
soils evaporate different amounts of water from their 
leaves; this difference, undoubtedly, is due to the 
conditions in the fertility of the soils, for the more 
fertile a soil is, the richer will the soil-water be in the 
necessary plant-foods. The principle that transpira- 
tion or the evaporation of water from the plants 
depends on the nature and concentration of the soil 
solution is of far-reaching importance in the develop- 
ment of a rational practice of dry-farming. 
Transpiration for a pound of dry matter 
Is plant growth proportional to transpiration? 
Do plants that evaporate much water grow more 
