344 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



white lead and boiled linseed oil. Bridge grafting may be used 

 where collar freezing occurs. 



Crotch injury. Associated with the winter killing of 1906-07 

 many of the injured trees showed the bark killed in the crotches 

 as illustrated in Fig. 238. A similar trouble was observed in 

 Ontario and other parts of Canada. There is some dijfference 

 of opinion as to just how this crotch injury was produced, but 

 there is no reason for regarding it other than as one form of 

 winter injury. This should not be confused with a similar 

 trouble caused by the pear blight bacillus which has been de- 

 scribed by Whetzel in New York. 



Frost hands on fruit. Occasionally late frosts occur which 

 are not sufficient to destroy the young fruit, but do result in a 

 peculiar characteristic russeting. As the apple enlarges and 

 approaches maturity this appears in the form of a band of vary- 

 ing width extending entirely around the fruit midway between 

 the stem and calyx. 



Frost injury of the leaves. Very frequently associated with 

 frost bands on the fruit there is more or less injury on the foli- 

 age. This has been described by Stewart and Eustace as fol- 

 lows : * 



"On the upper surface the leaves were variously wrinkled 

 and puckered, but the under surface was fairly even and normal 

 in appearance except for certain areas on which the color was 

 gray green. On some trees the leaves were badly distorted with 

 the margins drawn downward and together as if they were 

 unable to unfold properly. Usually the wrinkles were most 

 abundant along the mid-rib of the leaf and the elevated portions 

 were of a somewhat lighter green than the other parts of the 

 leaf. By cutting across the leaf with scissors it was found that 

 where the wrinkles occur the lower epidermis is separated from 

 the green, pulpy tissue (mesophyll), thus forming a large in- 

 terior cavity or blister. The distance between the green tissue 

 and the loosened epidermis was frequently as much as four 

 millimeters (one-sixth of an inch), and the blisters thus formed 

 were of all sizes up to those having an area of 100 square milli- 

 meters or even more. In many cases the separated epidermis 

 became ruptured as if slit with a knife, leaving the cells of the 



* Stewart, F. C. and Eustace. H. F. N. Y. Expt. Sta. Bui. 220, p. 218. 

 1902. 



