332 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



condition it should be in." We cannot, however, go so far as he 

 does in suggesting that for the sake of preserving close canopy, 

 even dead trees should often be left standing at the time of 

 thinning. A tree that is dead cannot contribute any appreciable 

 shade, and such a tree is a constant source of danger as a centre 

 for the spread of disease and injurious insects. Moreover, trees 

 that are removed as soon as they have died, or a little earlier, are 

 usually worth something, and go to swell the intermediate returns. 

 The main object of thinning is not the shortening of the period 

 of the struggle for the mastery that goes on between the dominant 

 and the dominated trees of a wood, but the utilisation of the many 

 hundreds of trees that find sufficient growing space on an acre 

 when say thirty years old, as compared with what the ground can 

 maintain a hundred years later. In a state of nature, such trees 

 die and rot on the ground, and yet the final crop is usually of the 

 vei'y highest quality. If, however, they had been judiciously 

 removed in the course of the rotation, the financial returns might 

 have been increased by a half, without interfering with the 

 technical quality of the final felling. 



Mr Simpson strikes the nail fairly on the head when he assails 

 the irrational use of mixtures. A few extracts will best illus- 

 trate his position. " Unfortunately the excessive number of 

 species included in British tree lists, and recommended for 

 planting, has been the cause of a great deal of indiscriminate 

 mixing, resulting in little else than trouble and loss in the end. 

 ... It may be asserted that probably nothing has tended more 

 to make the forester's task difficult in this country than the 

 indiscriminate mixing of species of greatly dissimilar habit. It 

 has caused endless trouble in thinning, and much pruning that 

 should never have been needed. . . . The English forester 

 wants to preserve his mixture as he began ; and to give weak 

 and strong a chance, he has to fight the battle with the pruning- 

 knife, without regard to overhead canopy." While recognising 

 the desirability of judicious simple mixtures under many, perhaps 

 most, circumstances, there can be no doubt that our English 

 mixtures are, as a rule, far too complicated. In too many cases 

 trees have been introduced without any regard to their sylvicul- 

 tural requirements. Oaks, spruces, alders, rowans, jostle each 

 other in a way that would, as the author says, "puzzle a 

 Continental forester, who does not contemplate such mixtures as 

 ours." Mr Simpson, as it seems to us, is perfectly right in his 



