CHAPTER I 



SOIL 



The functions of the soil in relation to plant life have 

 not yet been fully determined. Of late years this 

 [subject has received a good deal of attention, particularly 

 from American investigators, who have published the 

 results of their researches in the Bulletins of the Bureau 

 of Soils of the U.S.A. Department of Agriculture. In 

 publishing these results they have also propounded 

 theories which, however, have not been entirely accepted 

 in this country. Before giving a short account of them 

 it is necessary to relate what is known about the soil 

 and its functions which make it possible for plants to 

 grow in it. 



In order, namely, that a plant may exist and thrive 

 in a soil, it must be able to derive from it a sufficiency 

 of air, of water, of warmth, and of food ; it is also 

 necessary that there be in the soil no such injurious 

 substances as would poison the plant, and that the soil 

 be sufficiently tenacious to allow the roots to take a 

 firm hold of it and not to be pulled out by the action of 

 wind and surface water. 



All these factors are of equal importance ; a lack of 

 air is as detrimental to the plant as a lack of food, and 

 the presence of toxic substances will make an otherwise 

 fertile soil unfit for the growth of plants. Only, it 

 must be remembered that what is sufficient for one 

 species is not necessarily sufficient for another ; that one 

 species may grow in swampy land owing to its particular 



