12 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



No. 3 of the Forestry Commission, on the Rate of Growth 

 of Conifers in the British Isles, which gives us an interesting 

 table of the mean height-growth and volume production of 

 Douglas fir up to fifty years of age. The trees in the older 

 plantations are said to taper rapidly and have a low form- 

 factor. The authors, who did admirable work in the collection 

 of statistics under the Office of Woods and Interim Forest 

 Authority, suggest that the explanation of the low form-factor is 

 to be found in the previous history of the older plantations of 

 Douglas fir, most of them having been mixed with other species 

 which have been suppressed, or having been planted at wide 

 distances lo to 15 feet apart. They add that some of the 

 younger plantations, planted pure at distances of 4 to 6 feet, 

 show a higher form-factor. The authors do not seem to have 

 measured a sample plot planted at a less distance than 4 feet 

 apart: it is possible that closer planting might give even 

 better results. 



A great deal remains to be learnt as to the age at which 

 thinnings should commence in close plantations of Douglas fir. 

 On good soils the process of elimination of the weaker trees 

 has already begun at ten years after planting, and so long as 

 this process goes on energetically there may be no reason, for 

 the forester to interfere, unless for the removal of dead stems. 

 On less good soils it is quite possible that there may be over- 

 crowding at ten to twelve years after planting. 



With regard to the suppression of side branches, Sir Hugh 

 Shaw Stewart tells us, as the result of fifteen years' experience, that 

 the planting of Douglas fir at 3 feet apart does not prevent and 

 only partially restrains branch growth, and that if clean boles 

 are required hand pruning must be undertaken. The branches 

 are naturally wiry, and do not become brittle so soon after they 

 are dead as do those of larch and many deciduous trees. But 

 it is doubtful whether they differ much in this respect from the 

 branches of spruce and many other conifers. Certainly we 

 should not expect a thicket of spruce to begin cleaning itself at 

 fifteen years after planting. 



In a plantation of 2-yr. i-yr. Douglas fir at 3 feet apart 

 the side branches may begin to interfere with one another five 

 or six years after planting, the lower tiers die off quickly 

 between the seventh and the fifteenth years, but in the fifteenth 

 year none of them will have been dead for more than seven or 



