INDI VI D UAL ELEMENTS 



137 



ing nitrogen content correspond to those seasons when temperature and moisture 

 conditions are such as to favor nitrification in the soil. 



The percentage nitrogen content of j^oung fruit is very high. So also is that 

 of the seed, to which in fact the nitrogen content of the young fruit is in large 

 part due. In terms of drj' weight, the nitrogen content of apple seeds has been 

 found to be 3.17 per cent.; of almonds 4 per cent.; of coffee {Coffeo arabica) beans 

 1.96 per cent.; and of cocoanuts 1.65 per cent.^* 



In Various Tissues of Trees of Different Age. — A studj' of the nitrogen content 

 of trees of various ages will round out the picture of nitrogen distribution. 



Table 21 shows the percentages of nitrogen in the leaves, new growth, trunk, 

 roots and fruit of apple trees of ages ranging from 1 to 100. Since the material 

 was collected from various sources, the analyses are not strictly comparable, 

 though they are suggestive. 



Table 21. — Analyses of Apple Trees 

 (1 to 9 from Thompson,^^^ 13 and 100 from Roberts,^^' 30 from Van Slyke i*") 

 A Nitrogen in percentage of dry weight. B Absolute amounts of nitrogen in 

 gram.s. 



These figures show that the young tree is specially rich in nitrogen. The 

 roots have a higher percentage content than the trunk, but a lower content than 

 the new growth. The percentage nitrogen content of both roots and trunk falls 

 to a very low level in the 100-year old tree, due to the great preponderance of 

 woody tissue. That of the leaves was estimated from samples collected in the 

 fall and consequently is probably too low, except in the case of the 100-j^ear old 

 tree, where the sample was taken in July. 



The most striking observation to be made concerns the large proportion of 

 the total nitrogen of the plant that is in the leaves, roughly about one-fourth in 

 trees up to 9 years of age. Since these figures represent the amounts at leaf fall, 

 even larger amounts must be present in the leaves during the summer. 



