198 THE DEVELOPMENT OF BRITISH FORESTRY 



in May and June, and this liability to damage appears to 

 be as great with indigenous as Avith introduced trees. 

 Ash, beech, silver fir, oak, Spanish chestnut, walnut, Sitka 

 spruce, Douglas fir, etc., are all subject to this injury, 

 while sycamore, elm, poplar, alder, willow, birch, etc., are 

 seldom touched. Young trees, and those growing in 

 valleys or hollows, are the chief sufferers, while those 

 with tops twenty feet or more above the ground usually 

 escape serious injury. 



The effect of late frost damage, however, depends upon 

 the soil and situation in which the trees are grown. On 

 high-lying or sloping ground, and aspects facing away 

 from the rising sun, frost inflicts less injury than on cold, 

 damp soils, in hollows or valleys, and on eastern aspects. 

 These facts are well known and repeatedly confirmed by 

 experience, and practical men seldom plant, if they can 

 avoid it, localities subject to late frost with tender species. 



Probably the injurious effect of late frost upon trees 

 like ash, beech, silver fir, and oak is an inherited weak- 

 ness, due to the fact that they are seldom exposed to low 

 temperatures under natural conditions when in the young 

 stage. All natural regeneration, or nearly all, takes place 

 under the shelter of the parent trees, and it is not until 

 the trees attain a height of ten to twenty feet, or until 

 the parent trees are blown down or removed, that they 

 are fully exposed to frost attacks. 



Resistance to persistent wind as a specific feature is 

 chiefly conspicuous in sycamore, ash, beech, silver fir, 

 Corsican pine, Sitka spruce, etc., and is chiefly de- 

 ficient in larch, Douglas fir, Thuia gigantea, etc. Abso- 

 lute resistance to wind depends largely upon sunmier 

 temperatures and vegetative vigour, as influenced by 

 elevation and quality of soil, and also upon methods of 

 cultivation, such as density of cropping, etc. 



Liability to injur}- from insects and fungi is a very vari- 



