22 THE PLANT. 



of the foocl-absorbeut surface up to the fourth stage of 

 growth. 



The smallest increase was seen in phosphoric acid and 

 nitrogen, both equally necessary for the formative pro- 

 cesses going on in the turnip plant ; and it is manifest 

 that they must have served to bring into operation some 

 more powerful agency, whose effects are revealed in the 

 production and augmentation of the non-nitrogenous 

 constituents. 



If we take the quantity of mineral substances absorbed 

 as the measure of their importance for the organic opera- 

 tions going forward in the plant, we must assign to sul- 

 phuric acid and common salt an influence equal to that 

 of any of the others. 



Looking at the quantities of mineral constituents 

 severally taken up by the different parts of the plant in 

 the various stages of growth, we observe the greatest 

 disparities. In the second stage, a quantity of potash, 

 amounting in the aggregate to 49*29 pounds, was absorbed 

 in 35 days ; and of this, the roots were found to contain 

 8-02 pounds, equal to one-sixth — the leaves 41*27 pounds, 

 equal to five-sixths. The same proportion — namely, 

 about five to one —was found to exist between the weight 

 of the leaves produced, and that of the roots. 



In the third stage, the weight of the roots produced 

 exceeded that of the leaves ; and of the 80 pounds of 

 potash absorbed by the plants, 34 pounds, or more than 

 one-thuxl, remained in the roots. The same was found to 

 be the case with phosphoric acid, and the other mineral 

 constituents ; that is to say, they were found distributed 

 in varymg proportions, corresponding to the growth and 

 increase of the mass of the overground and underground 

 organs of the turnip plants, which, in the various stages, 

 are hkewise not uniform. 



