10 jSTov., 1917.1 Composition of the Potato Plant. 



649 



presence of an excess of soluble phosphoric acid in the synthetic soil 

 used in the experiment. 



Thirdly. — The small root harvest obtained by the German experi- 

 menters compares unfavorably with root figures herein published. 

 (Table I.). 



The loose, mellow, coarse sand, used as a soil in the local experi- 

 ment, was admirably suitable for root harvesting, l^o information is 

 given as to the soil used by the Germans. 



Notwithstanding these unsatisfactory features the experiments agree 

 on the important question, viz. : — Does the potato plant, dui'iug its 

 growth, return plant food constituents to the soil? The answer is, 

 No. 



Table VI. 



Analysis of the Potato Haulm at Various Harvests. 



All percentages calculated on absolute dry matter. ' 



Table VII. 



Amounts of Plant Foods in Pounds pee Acre, Contained in Haulm 



OF 12,000 Plants, at Various Harvests. 



Table VIIa. 

 Katio of Plant Foods in Haulm. 



The analyses of the potato haulm at various harvests show a marked 

 diminution (Table VI.) in the content of the three essential plant foods, 

 i.e., nitrogen, phosphoric acid, and potash, from the first to the final 

 harvest. The percentage of lime shows an increase towards maturity, 



