DISEASES. 1(J9 



sap have been excited by mild or warm weather, as is so 

 apt to be the case in our changeable climate, the sudden 

 depression of temperature will produce disastrous effects, 

 even when the cold has not been very severe. This is 

 manifested by the bursting of the bark in young trees in 

 the early part of winter, while they are yet holding their 

 . leaves, and of course having a circulation somewhat active. 

 Hence the importance, now very well understood by our 

 nurserymen, of checking the growth of young trees in 

 time to have their terminal buds thoroughly ripened be- 

 fore the approach of frost. This, to a certain extent, is 

 subject to our control; but we cannot foresee the charac- 

 ter of the seasons upon which the safety of our orchard 

 trees will, in a great measure, depend, and they are less 

 easily managed. When the autumn is dry, and continued 

 late into winter, as sometimes happens, we see a per- 

 fect ripening of the wood, with a great development of 

 blossom buds, and then we may confidently calculate up- 

 on the safety of our fruits, provided they be not exposed 

 to a warm period at mid-winter, that shall excite some ac- 

 tivity in their circulation, which would suffer terribly from 

 any sudden and great depression of temperature such as 

 frequently occurs, carrying the mercury from summer 

 heat to a point below zero, in a few hours. Such a change 

 has amounted to 68 degrees iu nine hours.* 



O 



The influence exerted by the soil upon the healthiness 

 or unhealthiness of our trees has already been alluded to 

 incidentally, but it is an important subject of inquiry 

 whether this may arise from a redundancy or a paucity of 

 some particular ingredients necessary to sustain the plants 



* Trans. Cincinnati Horticultural Society, 1SG5. 



