OBSERVATIONS ON VEGETABLES. 353 



It has been the received opinion that trees grow in 

 height only by their annual upper shoot. But my 

 neighbour over the way, whose occupation confines him to 

 one spot, assures me that trees are expanded and raised in 

 the lower parts also. The reason that he gives is this : the 

 point of one of my firs began for the first time to peep 

 over an opposite roof at the beginning of summer ; but 

 before the growing season was over, the whole shoot of the 

 year, and three or four joints of the body beside, became 

 visible to him as he sits on his form in his shop. According 

 to this supposition, a tree may advance in height considerably 

 though the summer shoot should be destroyed every year. 



FLOWING SAP. 

 If the bough of a vine is cut late in the spring, just 

 before the shoots push out, it will bleed considerably ; but 

 after the leaf is cut, any part may be taken off without the 

 least inconvenience. So oaks may be barked while the leaf 

 is budding ; but as soon as they are expanded, the bark 

 will no longer part from the wood, because the sap that 

 lubricates the bark and makes it part is evaporated off 

 through the leaves. 



EENOVATION OF LEAVES. 



When oaks are quite stripped of their leaves by chaffers, 

 tliey are clothed again soon after midsummer with a 

 beautiful foliage; but beeches, horse-chestnuts, and maples, 

 once defaced by those insects, never recover their beauty 

 again for the whole season. — White. 



ASH TREES. 



Many ash trees bear loads of keys every year, others 

 never seem to bear any at all. The prolific ones are naked 



314 



