Phillips — Hail Injury on Forest Trees. 53 



catalpa with the exception that the bark wounds on 

 catalpa were much more irregular because of the fibrous 

 nature of the bark. 



The deepest bark wounds on any species were found on 

 the cottonwood and box elder. This was due to the soft, 

 smooth nature of the bark which extends over compara- 

 tively large branches, while in such trees as catalpa the 

 bark matures rapidly. It was not infrequent to see 

 branches of cottonwood 3 to 4 inches in diameter with 

 wounds an inch broad and several inches long. Cotton- 

 wood was about one-half defoliated; the characteristic 

 injury consisting of riddled leaves which consequently 

 lost their function and were shed by the tree. A peculiar 

 character of the injury to the limbs consisted of wounds 

 bridged over by dead cortical strands of fibrous bark. 

 It is thought that the force of the hail was sufficient to 

 injure the cambium without entirely destroying the bark. 

 The possibility of fungus action was considered but since 

 no trace of fungi was found in such areas it was thought 

 improbable that the injury was due to such a cause. 



Honey locust suffered from defoliation but had only 

 slight injury to the wood. Black walnut was in most cases 

 entirely defoliated. The bark was wounded slightly more 

 than honey locust but not so much as box elder or cotton- 

 wood. Silver maple had slight injury both to the leaves 

 and the bark. Green ash leaves were less injured than 

 black walnut while the bark was injured about the same. 

 Russian olive leaves were scarcely affected and the bark 

 showed injury only in rare cases. Bur oak had no ap- 

 preciable injury to the bark and only a few leaves were 

 partially lacerated. 



Box elder suffered more from defoliation than did 

 cottonwood, but on the other hand more leaves were shed 

 and fewer lacerated. The wounds on the young wood were 

 as severe as on cottonwood. American elm suffered mod- 

 erately from defoliation and laceration, but had only rare 

 injury to the bark. English elm showed still less effect 

 on leaves and wood than American elm. White willow 

 suffered worse than sand-bar willow in both bark and 



