]^EW York Agricultural Experiment Station. 281 



there was alvv^ays one waiting at the rim of the hole. Tree 5/6 was 

 infested with fewer beetles, and since the injured trees were about 

 the same distances apart and similarly surrounded by normal ones, 

 it appeared to indicate a difference in the trees which had been 

 treated. As a matter of fact there was a slight difference in the 

 amount of dead foliage on the treated trees: tree 5/6 had least and 

 tree 2/9 had most of it. But nearly a third of the foliage of the 

 latter tree was still hving and appeared more turgid than it did two 

 days before. 



Since the bark on the treated trees was all alive and of normal 

 color (except some on the trunks near the ground) it is difficult to 

 understand how these beetles selected only the injured trees on which 

 to bore, unless it be by differences in turgidity or water content of 

 the bark though the presence of clumps of dead leaves may have 

 been a sign for attack. 



In this connection it may be of interest to note that D. H. Jones 

 has recently published an article* on Scolytus rugulosus as an agent in 

 the spread of bacterial blight of pear trees. 



observattons during 1912. 



The field observations during 1912 were mainly of a supplementary 

 nature. Observations had shown that the types of winter-injury 

 under consideration, which may result in crown-rot and cankers, 

 occurred sometime between the middle of November, 1910, and the 

 first part of January, 1911; also that after thawing and during the 

 following vegetative activities injured tissues become discolored and 

 more or less disorganized, leading to discoloration and death of some 

 adjoining and of all isolated live tissues. During the winter of 1911- 

 12 and the following summer, an effort was made to localize more 

 definitely the time of occurrence of these injuries in winter; to study 

 the histological modifications induced, and to make further observa- 

 tions on trees injured in winter of 1910-11. 



During last scholastic year observations were made in and around 

 Madison, Wisconsin, and after the first of June were continued in 

 New York. The histological study begun in the University of Wis- 

 consin had to be discontinued after arriving at the Experiment 

 Station on account of lack of necessary apparatus; but the field 

 observations and the fixing of material for the histological study were 

 continued. Since the material yet remaining necessary for a his- 

 tological study of the initial injuries and the subsequent changes 

 taking place in affected areas had been fixed and infiltrated with 

 celloidin, the gaps in the studies made in the University of Wisconsin 



^ D. H. Jones. Scolytus rugulosus as an agent in the spread of bacterial blight on 

 pear trees. 



Phytopath. 1 :155-58. 1911. 



