116 



EXPERIMENTS UPON EOOT-CROPS 



If one or other element necessary to the nutrition of the plant 

 be lacking, the root ceases to swell instead of altering its 

 composition to meet the deficiency. 



Table XLIIl. — Composition of MaiKjd Roots. Mean of two Seasons 

 (1900 and 1902). 



There are, however, certain differences in composition which, 

 if not large, are regular, and brought about l^y the differences 

 in manuring. Dealing with a series of roots which receive an 

 ample supply of mineral constituents, as on Plots 2, 4, or 6, the 

 size of the root and the proportion of water rise with each 

 addition of available nitrogen. The smallest and richest roots 

 are those grown without nitrogenous manure, the largest and 

 most watery are those wdiere nitrate of soda is used in con- 

 junction with dung. The roots grown with ammonium-sahs 



