38 transactions op royal scottish arboricultural society. 



Animal Agencies. 



Under this heading we may include insects, game, squirrels, 

 etc. 



The larch-moth caterpillar does much damage to the bursting 

 buds and foliage in spring. This is a time when the tree is in 

 gieat danger, because, in their early spring condition, the tender 

 buds and leaves are more easily damaged than later on in the 

 season. About the time the foliage is beginning to appear, the 

 larva awakens from its winter sleep, and begins to feed on the 

 young green leaves, and if the transition to the summer from the 

 winter condition is slow, the insect has a longer time in which 

 to do harm. Fortunately, however, this insect is not so pre- 

 valent in Scotland as on the Continent, and probably the damage 

 it does is of secondary importance when compared with that 

 caused by the larch aphis (Chermes laricis). 



The damage done by squirrels is often very serious, the peri- 

 derm being xorn off in long strips, leaving the tissue below 

 exposed and unprotected. Still, I don't know of any authentic 

 case where the canker has been observed to follow the ravages of 

 these destructive little animals. This is a point which might 

 be worthy of further investigation. 



Physical Agencies. 



Hailstones may do great damage to the periderm, and al- 

 though liail-stornis are more frequent and severe on the 

 Continent than with us, still the past summer has shown that 

 serious damage may be done by hail in this country. At the 

 January meeting of the Society in 1902, a number of speci- 

 mens wei'e exhibited, which showed clearly that hailstones may 

 cause wounds quite sufficient for the entrance of the fungus. 



Again, the accumulations of snow on the side branches may 

 cause them to bend down to such an extent that the periderm 

 is over-stretched and torn at the base of the branch, and this 

 may explain, in some instances, the appearance of the canker at 

 such j)]aces. Lightning may sometimes cause wounds of such a 

 nature as to facilitate the entrance of the jjarasite. 



Injuries caused by Man. 



In the packing of young trees in the nurseries, and in the 

 course of their transport to their destination, and also during 



