144 THE PRINCIPLES OF FLORICULTURE 



This tension holds the plant erect and when the moisture 

 in the soil is reduced so that there is not an equilibrium 

 between that taken in by the roots and the water which 

 is passing off through the tissue of the leaf, the plant wilts. 



Growth is, therefore, dependent on proper amounts of 

 soil water. This varies in different species. Some plants 

 are moisture-loving, while to others large amounts of soil 

 water are detrimental. The plant-grower should study 

 the peculiar needs of each particular species. 



110. The proper amount of plant food. The subject 

 of manures and fertilizers is considered in another chapter. 

 Only the principles which affect the absorption and assimi- 

 lation of food will here be considered. 



All food substances are taken into the plant in solution 

 through the roots, or in a gaseous form through the leaf 

 and other green parts of the plant. Those cultural con- 

 ditions which favor the absorption of liquids and gases 

 should be given plants, also the foods which are best 

 suited for the individual species, and the correct amount. 

 The diet problem in the human race and in animals has 

 received careful study for many years. Plant-growers 

 have only recently commenced to realize that the diet of 

 , plants should also receive consideration. 



To understand properly the principles affecting the 

 application of food, one should keep in mind that plants 

 take their liquid food through the root-hairs, due to the 

 fact that the denser liquid of the protoplasm has a strong 

 absorptive power for the less dense soil water. If soil 

 water is too highly charged with fertilizing elements, it 

 becomes more dense in character and the protoplasm of the 

 cell contents is drawn out, the root-hairs collapse and the 

 root dies. This is what occurs in saline soils and renders 

 them unfit for most plant growth. Fertilizers applied 



