TITS. 387 



by others. The injury which they do to the young buds, in 

 the very cores of which they batten, gradually brings on 

 that languid action in the tree, in consequence of which the 

 influence of the sun, which, in healthy plants, would bring 

 out a rich and luxuriant foliage, induces a saccharine con- 

 dition of the sap, which fosters the congregating caterpillars, 

 so that they appear upon the tree in swarms, secure, during 

 the day, in their silken tents, but eating voraciously at night, 

 till not a particle of green is left ; so that if the tree does 

 not perish, it remains actionless for the year. 



Nor is the mischief confined to the leaves ; for, without 

 their action, the sap does not change into a healthy cambium, 

 fit for producing the new layers of wood and of bark, which 

 when a tree ceases to produce, its decay is begun. The 

 whole active surface of the tree thus becomes saccharine, and 

 is infested with swarms of insects of different kinds, down 

 to the very roots; and in the course of the summer, the 

 bole and branches become full of ulcerated and cankering 

 sores ; half the top dies, branch after branch, and the 

 miserable remnant of the erewhile fruitful and ornamental 

 tree becomes equally unproductive and unsightly. 



When a tree is thus attacked, its recovery is always doubt- 

 ful, and generally hopeless. Wood and bark that have stood 

 more than one winter, are much less fit for vegetable action, 

 even though they have received no direct injury, than when 

 they have stood only one. But in a tree which has been 

 injured as above described, the continuity of even the stif- 

 fened vessels is broken, and the new production, even if the 

 tree lives, is wasted in unsightly gnarls and knobs, which 

 give further shelter and protection to insects, and also form 

 lodgments for water, which stagnates and rots the wood. 

 Heading down and grafting is generally only loss of time 

 and labour ; and the diseased remains inoculate other trees. 



Such would be the natural course with most trees, and 



2 c 2 



