INDIVIDUAL ELEMENTS 



133 



Table 16.— Nitrogen in Leaves of Apple, Pear and Cherry '^^ 

 (In percentage of dry weight) 



Table 17. — Nitrogen of Plum Leaves^" 

 (In percentage of dry weight) 



May 18, 1908 4.917 



May 27, 1907 3.809 



June 22, 1908 2.208 



July 14, 1909 2.917 



July 31, 1909 2.816 



Aug. 21, 1909 2.402 



Aug. 29, 1908 2.398 



Sept. 6, 1909 2.413 



Sept. 30, 1908 1 . 152 



Oct. 28, 1909 1.096 



very nearly balanced by the demands for new vegetative tissue and for the develop- 

 ment of the fruit and seed. The second period of decrease indicates rapid deple- 

 tion of the nitrogen content of the leaf, the withdrawal being much in excess of 

 the, amount supplied. This picture presented by the plum is fairly typical of 

 other deciduous fruits. 



On the other hand, the absolute amount of nitrogen in the leaves does not 

 decrease throughout the season. Table 18, showing grams of nitrogen in 100 

 apple, pear, cherry and plum leaves from July to October, brings this out clearly 

 and shows that the absolute nitrogen content of leaves does not decrease 

 materially until after September. In all probability it is increa.sing until August. 



T.\ble 18. — Grams of Nitrogen in 100 Leaves^ 



Apple 



Pear 



Cherry 



Plum 



July 14 



July 31 



Aug. 18, 21.... 

 Sept. 3, 4, 6. .. 



Oct. 7 



Oct. 23, 27, 29. 

 Nov. 4 



0.704 

 0.734 

 0.795 

 0.742 



0.232 



0.401 

 0.421 

 0.409 

 0.368 



0.121 



0.713 

 0.553 

 0.624 

 0.593 

 0.602 

 0.178 



0.555 

 0.477 

 0.376 

 0.389 



O.ISO 



A comparison of the data showing absokite nitrogen content with the data 

 showing percentage composition of the dry weight indicates that in young leaves 

 with their high percentage of nitrogen, growth and carbohydrate formation 

 proceed at such a rate as to reduce the percentage composition of nitrogen even 

 though the intake of nitrates during this period is greater than the outgo of 

 elaborated nitrogen. During July and August and sometimes later, the leaf 



