I^O THE NEW HORTICULTURE. 



because trees are irrigated there, and, consequently, always 

 make a normal summer growth ; they never rest entirely at 

 that season. Secondly, because they are never exposed to 

 the proper extremes of temperature in winter, the climate be- 

 ing cool, moist and uniform during that period, and the trees, 

 having performed their work throughout the long summer, 

 are content to rest. Having been brought mostly from the 

 east, the pear trees must necessarily have the blight bacteria 

 in their sap, but the extremes of heat, drouth, floods and cold 

 are lacking for their development. 



Now, lastly, why did blight break out in my pear orchard 

 in 1894, after years of bearing, and when a case was never 

 known in this section before ? But as the experience of this 

 orchard furnishes an absolute demonstration of my hypothe- 

 sis that blight bacteria exist at all times in all pear trees, in 

 perhaps a modified form and subject to certain conditions, 

 which, being given, they are capable of rapid as well as 

 almost infinite multiplication, I will defer the discussion of it 

 until the next chapter, when some experiments in pruning at 

 different times from spring until summer will also be given, 

 which go to show beyond all doubt that the proper, and, in 

 fact, the only time when any tree should be pruned is, though 

 contrary to general teaching, when the sap is in motion. 



