EFFECT OF THE DROUTH ON FOREST TREES 223 



with coal tar or thick lead paint in order to keep decay infection from 

 entering the wound. With lighter branches less precaution is necessary 

 to avoid wounding. 



RECOMMENDATIONS. 



Since each citizen can not be expected to devote enough time to 

 qualify as a city forester or as a tree expert, it seems desirable that he 

 delegate his authority over his street trees to a commission, provided 

 every other citizen do the same thing. In this way only can uniformity 

 and effectiveness in street decoration be accomplished. It is "a matter 

 of considerable importance from both an esthetic and a business stand- 

 point that our street trees can be given the care that is bestowed on 

 other street fixtures. 



EFFECT OF THE DROUTH ON FOREST TREES. 



Professor W. Morrill. 



LOSS OF WOOD PRODUCTION. 



Trees are impelled to observe a period of rest. The winter is usual 

 period for this phenomenon, but conditions may bring about suspended 

 growth, or rest, during the summer. Nothing within the tree induces it 

 to rest; outside conditions alone bring about dormancy. Drouth is a 

 condition that will cause a period of rest in summer, just as cold brings 

 about the period of rest in winter. 



Trees have a regularly recurrent dormant stage during winter. So 

 long have they and the progenitors of the present living trees been accus- 

 tomed, in our latitudes, to the winter rest that many species would still 

 observe the period of dormancy even if transplanted to the congenial 

 warmth and moisture of a hothouse. Yet in time the inherited tendency 

 to observe winter dormancy may be overcome, when the trees are kept in 

 hothouses, where outside conditions are maintained favorable throughout 

 the year, as has been shown experimentally with honey locust, boxelder 

 and black walnut. Environment thus becomes stronger than heredity. 

 Our trees would not suspend active functions of growth at any time of 

 the year if not forced to do so by unfavorable outward conditions. 



As winter approaches our trees prepare for it by forming terminal 

 buds and by shedding their leaves. During the drouth this summer the 

 trees made the same preparations, in a measure, and the shedding of 

 many leaves was very evident. Professor W. L. Howard of the Univer- 

 sity of Missouri relates in his bulletin entitled, "An Experimental Study 

 of the Rest Growth in Plants," that a young elm planted on the horticul- 

 tural grounds of the Missouri experiment station in 1903 made a good 

 growth up to the beginning of August of that year, at which time a 

 drouth set in and continued with such severity that the tree ceased to 

 grow. By September 1 it had formed terminal buds and auxiliary ones 



