III.] NITROGENOUS MANURES AND COMPOSITION 85 



When dealing with root crops like Swedes and 

 mangolds, the effect of large quantities of nitrogen 

 may be seen to some extent in an increased production 

 of leaf in relation to the root, especially in the case of 

 Swedes, but the variation thus induced is not great. 

 The root or bulb is to be regarded as a vegetative 

 part of the plant just as much as the leaf; the true 

 physiological maturity does not set in until the second 

 season, when the production of the seed takes place. 

 The Rothamsted mangold plots afford a good illustra- 

 tion, and Table XXIV. shows the production of root 

 and leaf and the relation betv/een them for several 

 plots which vary in the amount of nitrogen supplied, 

 in 1900, a year when a very uniform plant was obtained. 



Table XXIV. — Effect of increasing Nitrogen Supply on 

 Ratio of Root to Leaf. Rothamsted. 



The proportion of leaf is a little greater with the 

 excessive dressings of nitrogen applied to the last two 

 plots, but ^he variations are not great nor closely 

 parallel to the supply of nitrogen. When Swede turnips 

 were sown on the same plots in 1908 the increase of 

 leaf with the greater nitrogen supply was much more 

 manifest, as is shown in the last three columns of the 

 table. 



The effect of the large amounts of nitrogen upon 

 the vegetative development of the plant is more dis- 



