ON PEARS. 113 



deserves consideration. Comparative observations are wanted to make out the case for us; 

 but certainly there is some proof derived from the analogy of things, that vegetables may 

 be so far over-stimulated by certain manures, as to render them more susceptible to the 

 causes of disease. Analogy, however, must not lead us astray. A vegetable has but few, 

 if any, of the properties of the animal ; and we may not certainly conclude, that because 

 a good liver becomes fat and subject to gout and dropsy, that a tree, from an abundance of 

 food, will become corpulent and liable to perish from a surplus of food. 



A.nother important rule of practice which seems to be established, is that it is better to 

 wait until the termination of the disease, before the dead parts are removed. The rule 

 will enable us to save much of the tree which would be sacrificed if the limbs are removed 

 at random ; and since experience proves that there is no danger of an extension of dis- 

 ease from their remaining, the propriety of this course need not be urged. 



There is still another species of blight which attacks fruit trees. It might be called the 

 leaf blight, inasmuch as it first begins in the leaf. The branch does not necessarily 

 perish ; frequently it does. Most of the leaves curl, dry up and fall off"; if they all fall 

 off, the limb necessarily dies. This affection differs from the pear blight in this: the limb 

 maintains its color, except that it is dry. There is no appearance of gangrene ; and if one 

 or two leaves are saved the limb will not die. In the pear blight, which affects the limb 

 so remarkably, gangrenous patches are common, and the leaf seems to die from an 

 obstruction of the flow of sap. In the leaf blight, on the contrary, the death of the leaf 

 is the cause of the death of the branch, by checking the flow of the sap into the branch. 

 The elm is more subject to this disease than any of our forest trees, except the buttonwood. 

 The disease is confined to those, we believe, which are cultivated ; at least, they seem to 

 suffer more than those which have not been transplanted. 



[AOEICULTURAI. RZPOIIT — VoL. III.] 16 



