PHOSPHORIC ACID AND POTASH IN GROWING TUKNIPS. 37 



add together the quantities of nitrogen absorbed in the 

 last two stages, fifty-five days, we find a daily average 

 of 1'02 pound of nitrogen, which is very nearly the, same 

 as in the preceding stage of growth. 



The quantity of potash increased from the llth Au- 

 gust till the 1st September, in a somewhat higher ratio 

 than the amount of vegetable substance produced. 

 From the 1st September till the 5th October the in- 

 crease of the roots was nearly double what it had been 

 in the preceding stage, but this is explained by the 

 migration of the potash compounds from the leaves to 

 the roots. It is evident that the increase of potash has 

 a certain connection with the formation of sugar and 

 the other non-nitrogenous constituents of the roots, but 

 no definite proportion can be established between them. 

 The absorption of sulphuric acid increased uniformly in 

 the three last stages ; that of salt was a little greater in 

 the third than in the second and fourth stages. 



Without wishing to indicate the exact part per- 

 formed in the process of vegetation by these various 

 mineral substances, as also by lime, magnesia, and iron, 

 we remark that, except in the case of potash, the absorp- 

 tion of them was evidently uniform from day to day, 

 yet showing every day a trifling increase corresponding 

 to the daily increase of the food-absorbent surface up to 

 the fourth stage of growth. 



The smallest increase was seen in phosphoric acid 

 and nitrogen, both equally necessary for the formative 

 processes going on in the turnip plant ; and it is mani- 

 fest 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-nitro- 

 genous constituents. 



If we take the quantity of mineral substances ab- 

 sorbed as the measure of their importance for the 

 organic operations going forward in the plant, we must 

 assign to sulphuric acid and common salt an influence 

 equal to that of any of the others. 



Looking at the qualities of mineral constituents sev- 

 erally taken up by the different parts of the plant in the 



