Pure and Mixed Woods 43 



Such a mixture as this, however, has many serious defects 

 which it is well to consider. It has been cited in order to show 

 some of the principles which govern a mixture by single trees, and 

 the objections will illustrate a few points. 



The inclusion of the spruce is objectionable : firstly, because the 

 root-system of this species is dense and shallow, and it is stated by 

 some writers that the deep-rooted oak is deprived of a sufficient 

 amount of moisture, tending to produce the condition known as 

 " stagheadedness," that is, the dying of the upper branches ; secondly, 

 because the spruce is also an alternate Tiost of a plant-louse infecting 

 the larch ; lastly, in the association of larch and spruce, the larch 

 seems especially liable to the attacks of the larch canker. 1 



Also, it may be stated with truth that the larch would be out of 

 place on the class of soil where oak was intended for the principal 

 crop of timber. Unless the soil was a stiff clay, however, the sub- 

 stitution of the Japanese larch (L. leptolepis) would do away with 

 the objections urged, to a very large extent ; for a less free natural 

 percolation of water in the soil seems to be required by this species, 

 and also it is more immune from the larch canker. 



The ideal mixture of another species with oak, where heavy 

 oak timber is required, is beech. It is unfortunate that there is 

 little demand for beech timber in this country. 



1 This may be due to the fact that a soil suitable for spruce is not so for larch ; 

 moreover, the plant-louse (Chermes lands) causing wounds and generally lowering 

 the vigour of the tree, the larch becomes more liable to this disease. 



