834 The Trees of Great Britain and Ireland 



ture, December 1903, and of which an abstract appeared in Transactions of 

 Royal Scottish Arboricultural Society, xvii. 269. This was based on measurements 

 made in June 1903, by the late Mr. Pitcaithley, forester to the late Earl of Mansfield, 

 who selected two typical areas of -^ acre each, on which he counted and measured 

 the trees, of which he found eighteen on one and twenty-five on the other area, and 

 accurately measured the cubic contents of two trees, one of which contained 46.76 

 cubic feet and the other 39.49 cubic feet measured down to 3 inches diameter. 

 Dr. Somerville, assuming Mr. Pitcaithley 's measured trees to be average ones, 

 brings out the total cubic contents per acre by quarter-girth measure as 7977 cubic 

 feet, and comparing this with Dr. Schlich's estimate of 2934 cubic feet made fifteen 

 years previously, comes to the conclusion that the average increase per acre in that 

 period was no less than 336 cubic feet per annum. 



This in my opinion is a mistaken calculation, and if compared with the annual 

 increment of 1 50 feet per acre per annum in Lord Ducie's plantation and the results 

 of the measurement of Gunoak wood, both on better land than that at Taymount, 

 we must hesitate to accept it as even approximately correct.^ 



The important point to consider is how long these trees will continue to main- 

 tain their rapidity of growth, and what will be the value of the timber 1 My own 

 belief is that they fall off in their rate of increase ; that the larger ones will 

 continue to suppress and starve out the weaker ones, as they have already done 

 to a great extent ; and that the timber of Douglas fir grown in the country will 

 never compare in quality or value with the imported timber, which, it must always be 

 remembered, is from 200 to 300 years old, and selected both in the forest and the 

 mill from a very much larger quantity. 



Dr. Schlich writes me as follows: — "As to the quality of the Douglas fir 

 timber, I merely quoted what the late Mr. M'Corquodale told me. Since then I 

 have paid some attention to the subject and noticed that in timber from young 

 Douglas firs there is a considerable difference between spring wood and summer 

 wood ; hence I am sure, and in this I agree with you, that only trees of considerable 

 age will yield timber equal in quality to that of larch, if at all." 



There are other causes, which tend to make the production of clean, straight 

 timber difficult, in many situations and on many soils in this country, and which 

 should be considered by all who contemplate planting this species largely for profit. 



The first is its tendency to form large and spreading branches, which it shows 

 in a very marked degree. In order to prevent this, the trees must be crowded to an 

 extent which is only possible with success on soils of unusual depth, or on slopes 

 composed of rock which is sufficiently disintegrated to allow the roots to penetrate 

 deeply ; in which case they may clean themselves when they attain a height of 60 

 to 80 feet ; though I have never seen any in England which have naturally cleaned 



1 After this was in print I sent it to the Earl of Mansfield for his opinion, and am informed that in 1908 a carefiil 

 measurement was made by his forester, Mr. A. T. Kinnear, of the whole of Taymount plantation, which now contains 1536 

 Douglas firs on the whole area= 192 trees to the acre. These contain 51,456 cubic feet (under bark) or 6432 cubic feet per 

 acre, being an increase of 3498 cubic feet per acre since it was measured by Dr. Schlich in 1888, equal to about 134 feet per 

 acre per annum since it was planted, the rate of increase from 1888 to 1908 being about 175 feet. The largest tree is 93 feet 

 high, and contains 1 18 cubic feet. 



