HAIL INJURY ON FOREST TREES.* 

 Frank J. Phillips. 

 Among the minor injuries to which forest trees are 

 exposed that of hail storms is one of the most interesting. 

 The total amount of primary damage resulting from such 

 storms is always localized sharply and while this damage 

 may be temporarily great so far as the locality is con- 

 cerned, it is not ordinarily severe for a whole region or 

 for a whole state even for a series of years. Within the 

 limits of individual storms, forest growth as a whole is 

 more immune from serious effects than almost any other 

 crop with the possible exception of the short, non-culti- 

 vated grasses. Whole crops of fruit and vegetables are 

 often entirely ruined while forest trees usually escape 

 with varying amounts of defoliation, laceration of the 

 bark and cambium, and the occasional destruction of 

 young trees or sprouts. Many of the European texts con- 

 sider this injury limitedly and one authority 1 on hail 

 reports storms which were severe enough to remove 

 branches two inches in diameter. 



No other region in the United States presents as good 

 a field for such an investigation as does the middle west. 

 A large number of hail storms occur in adjoining states 

 but the states of the Plains may be rightly called the 

 hail storm center. Missouri and Nebraska have been 

 selected as good examples for this region. In both these 

 states hail is a typical late spring and summer phenome- 

 non, although such storms do occur in March, October and 

 November in Missouri. Hail has been reported during 

 the winter months, but this is probably pellets of snow 

 or soft hail without crystalline structure, the same as the 

 ' ' Graupeln ' ' of Germany. 



In Missouri 2 during April and May, particularly the 

 latter month, hail accompanies almost every thunder- 



* Presented by title to the Academy of Science of St. Louis. Decem- 

 ber 20, 1909. 

 1 On Hail. R. Russell. 1893. 2 Information supplied by George Reeder 



Section Director, U. S. Weather Bureau.' 



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