EVEN-AGED MIXTURES . 101 



occasioned by the removal of the over-crop, at any rate if 

 the latter be of any considerable size. In this connection, 

 it may not be out of place to state that Birch are the best of 

 all nurses. 



So again, mixtures by single trees, when every tree 

 differs from its neighbour, will seldom be successful ; for even 

 if the trees have relatively the same height growth, one class 

 that is, one-half the crop will be of very bad quality if 

 there be a great difference in the mutual pruning of each 

 other. 



For instance, suppose a mixture of Larch and Corsican 

 Pine be planted, and that one keeps pace with the other. 

 The Larch will all be excellently pruned, but the Corsican 

 Pine will, every one of them, be branchy and knotty, as the 

 Larch will exert no effect upon them whatever. Often it is 

 thought prudent to introduce into a mixture a valuable 

 species whose success as a pure crop is doubtful. In such a 

 case, it should be introduced sporadically, perhaps one tree 

 every 1 6 feet apart, and the majority of the crop, known 

 as the "ruling" species, should consist of trees which will 

 prune the valuable species correctly, but will not overtop 

 them. In such a case, the welfare of the valuable species is 

 the chief consideration. Its success will more than counter- 

 balance any loss in technical value of their neighbouring 

 trees, which, even if the valuable species fail, will only form a 

 small proportion of the whole crop, and can be removed as 

 thinnings. 



For instance, it might be desired to grow some Larch on 

 cold flat land, but the chances of disease are far too great to 

 risk a pure crop. But, it would be a perfectly legitimate 

 gamble to plant Larch at intervals of 20 feet, and to have all 

 the rest of the area pure Scots Pine. 



The great difficulty of planting mixtures by single trees 

 or by alternate rows, and at the same time obtaining good 

 results for a fair proportion of the crop, cannot be too strongly 

 insisted upon. 



The old-fashioned promiscuous " nurseryman's " mixtures 

 must for ever be abandoned. The greater the number of 



