174 AMEEICAN POMOLOGY. 



disease. A very important question has arisen, however, 

 as to whether the inroads of fiingi -were the cause or the 

 consequence only of disease. A question which it will be 

 necessary to leave to wiser heads, only obsendng that 

 these epiphytes do appear, under certain atmospheric con- 

 ditions, to invade some plants that had previously seemed 

 to be in perfect health. That they are transported upon 

 the air, in the form of very minute sporules, is unquestion- 

 ed, and that their growth is dependent upon certain at- 

 mospheric conditions, is equally admitted, but whether 

 they induce disease, or are only able to take" possession of 

 a plant that is not in a perfectly healthy condition, does not 

 yet appeal" so clear. The very eminent Mr. Solly is of 

 the opinion, that in the potato at least, the existence of 

 parasitic fungi is a secondary result of previous disease. 

 So it may be with our fruits, and there is considerable tes- 

 timony to favor such a belief in many cases, where we 

 find, with the appearance of these fungi, other causes of 

 unhealthiness. 



The leaves of the apple trees in some seasons become 

 coated with a black efflorescence, that gives the tree a very 

 sombre appearance, and seems to affect its health. I am 

 not aware that any one has yet made any microscopical 

 investigations of this condition of the foliage, which looks 

 as though it were dusted with coal-smoke. It has been 

 supposed, however, to be the result of a fungous growth. 



Peab Blight. — This is a subject upon which so much 

 has been said and written, that any one may well shrink 

 from its discussion. The condition in which the invasion 

 of the malady finds the tree has been pretty thoroughly 

 ascertained, and the sad state in which it is left after the 



