10 Nov., 1(U7. 1 Composition of the Potato Plant. 



651 



Table IX. 



Pounds of Pl.vnt Food Contained in the Tubers Obtained pee Acre 

 (12,000 Plants) at Various Harvests. 



Table IXa. 

 Plant Food Ratio in Tubers. 



Pliosphoric 

 Acid. 



Nitrogen. 



Potash. 



Magnesia. 



Ist harvest 

 2nd harvest 

 3rd harvest 

 4th harvest 



2-3 



4-8 

 3-(i 



4-(i 

 4-0 



•15 

 •1 

 •2 

 •2 



The foregoing tables, relating to the tuber, are noted for their even- 

 ness. After the first month's development the composition of the potato 

 tuber shows a practically constant composition as regards essential 

 plant foods. In the early stage of formation concentration necessarily 

 furnishes a higher analysis. This is most marked in the case of phos- 

 phoric acid and potash. 



The amounts of plant food per acre (Table IX.), as would be expected 

 show a gradual increase throughout. In this table is seen once again 

 the remarkable relation between the lime and magnesia. 



The Ratio Table IXa., excepting the second month's retui-n for potash 

 (which, as in evei-y other case, was obtained in duplicate), is very even, 

 and strongly suggests a distinct relation between the amounts of the 

 various plant foods required for the formation of a given amount of 

 potato tubers. 



It will be noticed that the ratio in the tuber is entirely different to 

 the haulm ratio. (Tables VIIa and IXa.) 



Table X. 

 The Potato Roots — Composition at Various Harvests. 



