68i 



bundles, either because of an energetic influence due to adjacent and com- 

 municating protoplasts, or of a material transportation by means of sieve 

 tubes and analogous elements throughout the entire body ; they reach at last 

 the developing petioles and then the main ribs of the leaves. Here they 

 influence all the parenchyma cells with which they are connected clearly 

 more energetically or because of a poor nutritive provision, and removal." 

 The transference of the phenomena from the scion to the stock, therefore, 

 comes about if, in grafting, the leptome connection in the two component 

 parts has been established. 



This theory is based on experimental studies. It has been proved by 

 chemical investigation that "the protoplasm and plastids are gradually 

 attacked by abnormal formations of strongly destructive enzymes and 

 digested by them." In some intensive cases of albinism no accumulations, 

 however, of inorganic, or organic substances, or sugar, may be proved. 



A determination made by Pantanelli on Ulmus leaves throws light oh 

 the behavior of the nitrogen compounds. He pulverized green and non- 

 pigmented leaves with the necessary precaution and let the pulp stand 8 

 days in a cylinder. The original amount of water in the green leaves 

 averaged 60.67 P^^" cent., that in the non-pigmented leaves of the same tree, 

 at the same time, 73.8 per cent. 



The green leaves contained (in percentages of the dry weight). 



In the beginning After 8 days 



Nitrogen as a whole 3.355 per cent. 3-3250 per cent. 



Proteid nitrogen 3-324 " 0.9212 



Non-proteid nitrogen 0.031 " 2.4050 



Non-pigmented leaves contained (in percentages of the dry weight) : 



In the beginning After 8 days 



Nitrogen as a whole 2.681 per cent. 2.576 per cent. 



Proteid nitrogen 2.274 " 0.604 " 



Non-proteid nitrogen 0.407 " 1-972 



Autolysis in the sap of the variegated leaves is, therefore, compara- 

 tively more extensive than in the green ones. The amount of nitrogen in 

 non-pigmented organs is considerably less, but the percentage of non-proteid 

 nitrogen compounds is greater. The richly abundant phosphoric acid must 

 be present jn some other combination since lecithin cannot be formed nor 

 the chloroplast be developed. Also, according to Pantanelli's investigations, 

 an enzyme which breaks up the starch seems to be present more abun- 

 dantly in the variegated leaves than in the green ones, at least when they are 

 young. 



In the second edition of this manual (p. 195), I have already referred 

 to the nitrogen poverty of the non-pigmented parts and there- expressed 

 the following opinion : — in the normally nourished leaf cell so much cyto- 

 plasm is present that not only material can be furnished for the develop- 

 ment of the cell wall, but the chloroplasts can also be produced abundantly. 



