285 



have proved, however, that, besides this lack of additional growth, a positive 

 loss in substance takes place, which is much greater than in normal fall de- 

 foliation. The leaves killed by blight do not behave as do those which drop 

 ofif in the fall. These have gradually given up to the trunk most of the sub- 

 stances still utiUzable for the plant body and in the end have been loosened 

 l)y a round-celled layer of separation. The dried leaves, in which no such 

 layer has been formed, retain the elements which contain nitrogen together 

 with phosphoric acid and only the starch with the potassium reaches the 

 trunk before the death of the leaf. By the premature drying of the foliage 

 approximately twice as much nitrogen and phosphoric acid are, lost to the 

 plant as by the autumn leaf-fall. This is proved by analysis of the leaves 

 of a syringa carried through by Maerker. 



In percentages of dry substances, there was contained in 



Summer blighted leaves Autumn fallen leaves 



Nitrogen 1-947 i-370 



Phosphoric acid 0.522 0-373 



Potassium 2.998 3-831 



Calcitun i .878 2.416 



All mineral substances 



(free from carbon dioxid) 8.028 9.636 



The above amounts, if expressed in percentages of the whole ash, would 

 be as follows : — 



Summer blighted leaves Autumn fallen leaves 



Nitrogen 24.0 14.0 



Phosphoric acid 6.5 3.8 



Potassium 37.3 39.7 



The Burning Out of Grass. 



With the drying of the turf, as the result of hot periods in summer, the 

 loss of nutritive substances must be considered especially in meadows. 

 Where there are no irrigating arrangements, there is no possibility of avoid- 

 ing the injury. In ornamental planting, however, it may be avoided if the 

 action of the light and thereby evaporation is repressed at the right time by 

 mulching with hay or other light shading material. Sprinkling the grass 

 surfaces is effective only when it can be carried out repeatedly during the 

 day. In other cases, shading must be resorted to. 



Silver Leaf. 



The "Silver Leaf" belongs among the phenomena which have not yet 

 been tested experimentally in regard to their causes and therefore can be 

 classified only provisionally. 



The disease so manifests itself in fruit trees that the leaves, otherwise 

 normally developed, lose their dark green appearance and give a silvery, 

 whitish reflection. As a rule only individual branches sufifer and possibly 



