12 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



larch ; but where the Sitka spruce had been mixed in the 

 proportion of about a thousand plants to the acre the spruce in 

 turn had mostly been suppressed by it before the seventeenth or 

 eighteenth year after date of planting. At an altitude of about 

 750 to 800 feet, where the best soils occur, the Sitka spruce 

 has now reached an average height of from 46 to 50 feet, 

 with an average diameter at breast-height of 8^ inches, while 

 a proportion of the larger stems contain from 15 to 16 

 cubic feet. The average cubical content, arrived at by the 

 measurement of all the stems standing on an area of half 

 an acre of average growth, proved to be 6h cubic feet. 

 Against those averages it may be pointed out that the tallest 

 Norway spruces in the whole plantation do not exceed 35 feet 

 in height, nor do they reach the average diameter of the Sitka 

 spruce, while their average size, even in the very best parts, is 

 merely that of small poles (see Plate I.). 



Owing to the irregular way in which the trees stand on the 

 ground, they are, as may be seen from the above measurements, 

 also somewhat irregular in size, and as they stand with too 

 much head room, they have developed unduly spreading crowns. 

 They have, however, divested themselves of the suppressed 

 branches on the lower part of the stem to a much greater 

 extent than the more shade-enduring Norway spruces have 

 done under similarly dense conditions of crop. As the result of 

 carefully selecting and measuring a number of trees, typical in 

 form, and each standing on an area of thirty-six square feet (which 

 gives 1 2 10 trees to the acre, a normal density for Sitka spruce up 

 to the fortieth year), I have good reason to believe that, on suit- 

 able soils and with a full stand of trees on the ground, a volume 

 of 6000 cubic feet per acre is well within the possible timber- 

 production of this tree at thirty-one years after date of planting ; 

 and that by the time the fifty-fifth year has been reached, this 

 volume will have increased to 10,000 cubic feet, representing a 

 money value, at the rate of 6d. per cubic foot, of ;^25o per acre. 

 If judged by the rate of growth of Norway spruce, this volume 

 may appear well nigh unattainable ; but the fact must be 

 remembered that for Sitka spruce, as for Douglas fir, no 

 yield-statistics have as yet been compiled, and tables dealing 

 with the ordinary commercial forest trees are valueless as 

 an index of \vhat either of those trees are capable of producing 

 under cultivation. But while Douglas fir would give generally 



