344 PLAIN AND PLEASANT TALK 



frost upon the sap. We have, until recently, supposed it 

 to arise from autumnal freezing, while the tree is in full 

 growth. We are now inclined to suppose that severe freez- 

 ing and sudden thawing at any time, autumn, winter or 

 spring, when the sap is in motion, wiU result in blight. 

 The blight of 1844 was from the freezing of growing trees 

 in the autumn of 1843, and the premonitory stages were 

 clearly discernible in the tree during the whole winter 

 months before it broke out in its last malignant form. 



When a warm winter allows continuous motion of sap, 

 and sudden, severe freezing with rapid thawing occurs, we 

 suppose it to cause a variety of blight. We are making 

 investigations on this head, but are not yet prepared to 

 speak with certainty. 



When a sudden violent freezing overtakes growing trees 

 in spring, with rapid thaws, it, we suppose, results in a 

 blight resembUng the autumn-caused blight. 



We are diligently searching into this whole matter, and 

 hope to throw some light upon it. 



But now comes the question. What is it that makes 

 some trees so obnoxious to this evil while others escape ? 

 Why are some orchards generally affected, and contiguous 

 orchards entirely saved ? 



It is very plain that the blight occurs, as a general disease, 

 in some seasons more than in others, because it depends upon 

 the peculiar condition of the season, the time and degree 

 of frosts. But it does not seem so clear why, when these 

 conditions are favorable to blight, one tree should suffer, and 

 the next in the row should not ; why one orchard should 

 be depopulated, and another in the same town not touched. 



We think that light will be afforded on this point by a 

 consideration of the texture of trees. 



When trees are rapidly grown by stimulating manures, 

 or upon strong clay loams, or from any other cause, the 

 wood is coarse, the passages enlarged, the tissue loose and 

 spongy. The tree passes a great volume of sap — it is but 

 imperfectly elaborated (as is seen by the late period to 



