145 



that per 1,000 lbs. the older leaves contain 1*5 lbs. more potash than the 

 j-ounger leaves. On com])aring- the amounts of potash obtained in these analyses 

 with the quantity as found in leaves of other trees it is at once apparent that the 

 leaves of the apple tree are exceptionally rich in this material . 



"_Z/ime. — Tlie average percentage of lime in the ash of the young leaf is 1*7"40, 

 while that of the maturer leaf is 27'91, an increase of 10 per cent. This increase 

 would appeal- also to be regular throughout the varieties examined. Thus, the 

 Duchess stands first in percentage of lime in both lists, followed closely by the 

 Tetofsky, and so on. 



''Magnesia. — While the percentage of lime increased during the growth of the 

 leaf, the anal^'tical data show that the percentage of magnesia decreases during that 

 period. Thus, in the young leaf we have magnesia 9'77 as the average percentage, 

 and in the maturer leaf this number is reduced to 4-81. This fact is the more 

 remarkable and interesting when we remember that the percentage of phosphoric 

 acid diminished in the same ratio during the same period. It seems quite possible 

 that these two elements of plant food are intimately related in the economy of the 

 plant, and that in the elaboration of the plant food within the tissues and the dis- 

 tribution of this food to the different parts of the tree these two play a very 

 important role. 



" Oxide of Iron and Silica. — Throughout the whole series the amounts of these 

 constituents aie seen to be very similar, and the average in the young and the mature 

 leaf closely approximate each other. The iron after it has performed its functions in 

 the chlorophyll of the leaf appears to remain in the leaf, and from the ligujes in 

 the table it is seen that there is no extra deposition of silica in the cells of the leaf 

 as it grows older. 



^'Nitrogen. — The only constitutent of great importance that remains to be dis- 

 cussed is nitrogen. The differences in the amounts of nitrogen contained in the 

 organic matter of the leaves of the different varieties examined are so small that one 

 would not be warranted in drawing any conclusion therefrom as to differences in this 

 constituent between the varieties." On taking the averages, however, of nitrogen of 

 the leaves in the two stages of their growth, a considerable difference is at once 

 apparent — a difference that corresponds to 3 per cent, of albuminoids. The figures 

 are : — 



Nitrogen in young leaf 2-94 corresponding to 18-61 per cent albuminoids, 

 do maturer leaf 2 -48 do 15-50 do 



" The amount of nitrogen per 1,000 pounds of the maturer leaf is 8*87 pounds, 

 as against 7'42 pounds in the young leaf. This is due to the increased percentage of 

 organic matter in the older leaf. It is evident from these results that changes which 

 aftfect the relative percentage of nitrogen in the organic matter take place in the leaf 

 during its development — but what these changes may be is beyond the scope of the 

 present paper to discuss. 



" Phosphoric acid, potash and nitrogen are the three constituents which above all 

 others must be put back into the soil if we are to preserve its fertility. Plants of 

 certain orders require more of one or other of these than plants of other orders. 

 Some soils are specially rich or poor in one or more of the materials — and con- 

 sequently in the rational mode of application of fertilizers much intelligence and 

 patience must be exercised. 



"That the leaves of the apple trees draw a large amount of food from the soil 

 annually has been shown. This must be replaced in excess for the vigorous growth 

 of the tree. The leaves of the tree play no unimportant part — respi ration and diges- 

 tion are their two chief functions — which, if they do not perform well, the tree can- 

 not live and bring to perfection its fruit. Therefore when we feed the leaves we are 

 indirectly feeding the fruit. 



" The results of this work seem to point in the direction of mineral fertilizers, 

 and specially of potash, as being more particularly oquired foi- the gn^wth of the 

 leaves, and, therefore, for the vigorous developmciiit of the tree, including an 

 abundant crop of fruit. 



6c— 10 



