THE NEW FERTILIZATION. 105 



vegetation of a single acre draws from the soil in the course 

 of a brief season, from one-eighth to one- fourth of a ton for 

 every pound of dry substance produced, and that all but a 

 r.vnall fraction of this water is simply passed through the plant 

 from its roots where it is taken in to its leaves where it is ex- 

 haled, we cannot doubt that the process has much to do with 

 the carrying in of certain tissue-building material ; but this 

 does not account for the presence within the plant of those 

 substances like silica, phosphorus, nitrogen, etc., upon which 

 water exercises no solvent action. 



There are three forces which may be considered as capable 

 of effecting the primary changes in these difficultly soluble sub- 

 stances : plant secretions, the "vital activity" and soil bacteria. 



It was formerly believed that the resistant substances were 

 broken down by the action of the secretions and juices of the 

 plant ; that these materials, coming in contact with those por- 

 tions of the plant which project into the soil, in some manner 

 not clearly explained drew them into the plant body, where 

 they were then acted upon and digested and rendered suitable 

 for tissue building in some such manner as the gastric juice 

 and the succns intericus of the animal body digest and render 

 available for tissue building the various food substances upon 

 which they operate. In the light of present knowledge, how- 

 ever, it is no longer reasonable to suppose that a particle of 

 mineral matter, however minute, could be normally drawn 

 into the plant by any conceivable process of suction or absorp- 

 tion. A preliminary decomposition must take place, but the 

 secretions of a plant, though they escaped to the surface and 

 were found like perspiration upon the rootlets, we have no 

 reason to believe would possess the power of effecting such 

 a transformation. The sap, circulating within the plant as 



