STATE HORTICULTURAL SOCIETY. 47 



diseases and injuries of plants and animals are parasitic in their 

 nature; but it becomes more and more certain that all communicable 

 ones are due to living, growing and multiplying things. 



I wish, however, to be well understood in regard to })ear blight. 

 Bacteria (•<(!< sc the disease, if we s])eak of the immediate and active 

 agent in the change which takes place in the aifected tissues; that 

 is, the death of the parts is directly due to the work of a single and 

 certain species of these microscopic organisms. But if we speak of 

 the peculiarities of the tree, which i)ermits or favors the operation 

 of tliese minute enemies, as the cause, then we all agree that the 

 latter has not been well worked out. No one, I venture to assert, 

 can tell why a Bartlett or a ria])])'s Favorite blights, while in the 

 same soil and under the same conditions a Duchesse d" Angouleme, a 

 Tyson or Seckel does not. We speculate about vitality, maturity of 

 growth, predisposition, resistance, etc.; but speculation is not demon- 

 stration. We talk, and perhaps learnedly, about the effects of tem- 

 perature, high or low, electricity, thunder and lightning, drainage, 

 soil, potash, lime, rusty iron, salt, cultivation, grass, etc., etc.; but 

 when it is all done we must acknowledge that the basis of proof, if 

 there is any so far furnished, is the merest em])iricism. and at any 

 time liable to overwhelming contradiction. For one, however, I have 

 faith in science, and confidently look for answers to some of these 

 deeper-lying questions from the physiologists and chemists, guided and 

 aided by the critical observations of practical cultivators. It is by 

 no means impossible that we shall yet know what the real essence of 

 vitality and hardiness is, whether material or immaterial. 



I repeat- the direct or immediate cause of the disease we call 

 blight in the pear and apple-trees is a specific, named and described, 

 living organism belonging among the bacteria, and which can be in- 

 variably found in the blighting tissues as surely as bees can be found 

 in hives containing honeycoml) in })rocess of construction. Beyond 

 this confideiit assertion of the fact I do not now care to go, save 

 some account of prevention to be given further on. 



I turn now to the disease called yellows of the peach-tree. After 

 the researches upon the peach-tree blight had been publiidy reported, 

 specimens were sent me from Detroit and South Haven, Mich., from 

 what pur])orted to be peach-trees suffering with yellows. The dis- 

 ease was and is notoriously prevalent in the latter district. Three 

 distinct lots of specimens were received, and after a careful examina- 

 tion of them it seemed to me that the conclusion was warranialde 

 that the cause of the well-known contagious malady was an organism 

 found in the affected tissues, not very unlike that of blight, in the 

 ■pear. This conclusion a])peared in pul)lic ]irint, ])erhaps prematurely. 

 The three lots of sjjecimens were the only ones examined. No ex})eri- 

 ments of inoculation, etc., were tried; no living and growing trees 

 were seen suffering with the disease. Now, nothing su])j)()rting the 

 " bacteria theory " of the yellows has come to my kncnvledge; no 



