PEACH AND TIIK TEAR. 2/3 



these severe forms of blight as follows, but he docs not 

 go far enough to find the real cause : In every tree 

 there are two currents of sap. one up, through the outer 

 wood or alburnum to be digested by the leaves, the other 

 downward, which descends through the inner bark or 

 liber, forming a deposit of new wood on its passage down. 

 Now the summer before the tree blights, is followed by a 

 damp and warm autumn preceding an early and severe 

 winter. • The summer was dry and the wood growth was 

 completed early, but the damp, warm autumn forced the 

 tree-wood to a second growth, which continued late. 

 Now while the sap vessels are still full of their fluid, a 

 sharp freeze comes, and this is repeated for several nights, 

 followed in the day time by bright sun. The descend- 

 ing current of sap becomes thick and clammy so as to 

 come down with difficulty ; it chokes up the sap vessels, 

 freezes and thaws again, loses its vitality and becomes 

 dark and discolored, and in some cases so poisonous as 

 to destroy the leaves of other plants when applied to 

 them. Here, along the inner bark, it lodges and remains 

 thick and sticky all winter. If it happens to flow down 

 until it meets with any obstruction and remains in any 

 considerable quantity, it freezes again beneath the bark, 

 ruptures and destroys the sap vessels, and the bark and 

 some of the wood beneath it shrivel and die. In the 

 coming spring the upward current of sap rises through its 

 ordinary channel, the outer wood or alburnum, the leaves 

 t8 



