138 SCIENCE IN FORESTRY 



that the capital expense of planting is lying out 

 at compound interest throughout the rotation, 

 and if that extends beyond a certain period the 

 result will be loss instead of gain. There is a com- 

 mon belief that all quickly grown timbers are of 

 inferior quality. This is not the case; it holds 

 good only as regards durability in the case of 

 coniferous timber, but does not hold good in 

 respect of any quality in ash, oak, and walnut. 

 Further, as regards the conifers it is now possible 

 artificially to increase the durability of the most 

 inferior to a point which makes them far superior 

 to the naturally durable timbers untreated. With 

 oak, ash, walnut, etc., the quicker their growth, 

 the better is their quality in every way. They 

 are more durable, more elastic and less difficult 

 to work. Further by hybridizing it may be possible 

 to produce disease-resisting varieties, and varieties 

 carrying with them other desirable characteristics. 

 The small amount of work already done in the 

 way of hybridizing serves to prove the possibilities, 

 and distinctly points the way to scientific dis- 

 coveries of great value. 



What is true of plant diseases, is equally defi- 

 nitely demonstrated in the case of insect enemies. 

 The artificial forest favours the rapid multiplica- 

 tion of the insects which prey on trees. Ideal 

 breeding and feeding grounds are provided, and the 

 natural enemies of the insects are often destroyed. 

 It is on record that in the period 1892-96, more 



