122 THE NEW HORTICULTURE. 



to suppose, on the external theory, that the whole atmosphere 

 is alive with the bacteria of blight ? Again, as a rule, blight 

 develops worst on the most vigorous, healthy trees, in clean, 

 cultivated ground? How shall we account for this, when all 

 experience with man, animals and trees, under the attacks of 

 insect pests, goes to show that the strongest and most vigor- 

 ous always best resist injurious attacks ? Again, why, if the 

 bacteria of blight are in the air and attack from the outside, 

 does any tree escape ? All are equally exposed, and the 

 weakly tree should certainly succumb as readily as the strong. 

 But the hypothesis that these bacteria are in and a part of all 

 pear and apple trees in limited numbers, and, under certain 

 normal conditions play, perhaps, a specific, useful part in the 

 life and development of the trees, will cover and explain all 

 the phenomena of blight. A contrary supposition demands 

 the belief in an actual creation one hundred years or so ago, 

 when this disease first appeared, else why were pear and 

 apple trees never attacked before ? Simply because the con- 

 ditions for their development in destructive numbers had 

 never been furnished. That the eastern half of the United 

 States, say from Kansas and Texas to Canada, with its ex- 

 tremes of wet and dry, heat and cold, often in rapid succes- 

 sion, present ideal conditions for all bacterial diseases of 

 trees, there is no doubt, and if there is a region in the world 

 where they could originate it would be there. I have often 

 wished that we knew the exact history of the trees upon 

 which blight originally appeared in New England, from the 

 time they were planted until the disease broke out. I think, 

 however, it would read somewhat thus : 



The ground was deeply plowed, well pulverized and ma- 

 nured, or naturally rich, and the trees when set were about 

 three years old, well provided with long as well as fibrous 

 roots, which were nicely spread out in large holes. They 

 were then well cultivated and cared for, especially in the way 

 of a good plowing every year, until they came into bearing, 

 the first light crops being very fine, and when loaded down 

 with their first very heavy crop, all of which the owner left 

 on, the season turned out very dry. Being largely surface- 



