Exotic Conifers in Britain. 



325 



that for any given age, their girth at breast-height is greater 

 than would be the case with trees of a similar age grown in 

 close forest. On the other hand, the height is probably less 

 than it otherwise would have been. The circumference is 

 given at 4J feet from the ground. The ages given are calcu- 

 lated from the time of planting, at which time the tree would, as 

 a rule, be four years old, so that to get the actual age from the 

 time of sowing the seed the figures would generally have to be 

 increased by four. 



The dimensions given for the various species are not averages, 

 but are the result of actual measurement of individual trees 

 situated in the districts indicated. As a rule, for any given age, 

 the largest tree has been selected. Some may think that this 

 is not a fair index of what a particular species may be expected 

 to attain to at any given age, but I am disposed to think that 

 the maximum height recorded for a certain age, in the case of 

 a tree grown in a garden or park, is more likely to represent 

 what may -be looked for, when the same species is grown in 

 close forest, than the average height of all the trees of that age 

 would be. It is to be remembered that the figures that follow 

 are taken, for the most part, from " specimen " trees, and that 

 in their case there has been little application of the law of the 

 survival of the fittest. Suppose that forty years ago an order 

 was given to a nurseryman for five Douglas firs about 3 feet 

 high, the plants supplied might vary from three to six years of 

 age. A Douglas fir that attains the height of 3 feet in three 

 years may be regarded as an individual with a natural tendency 

 to vigorous growth, whereas if six years be taken to reach 

 the same height the particular individual is manifestly a slow 

 grower. If the five Douglas firs were intended for landscape 

 effect, each would be set out with abundance of room, and, no 

 matter whether it grew fast or slow, it would be allowed to sur- 

 vive. At the end of forty years the tallest of the trees might be 

 80 feet, while the smallest might not exceed 40 feet, giving an 

 average of, say, 60 feet. But if a number of Douglas firs were 

 planted 3 or 4 feet apart, and managed in true sylvicultural 

 fashion, the only individuals that would survive to the age of 

 forty years would be those with a natural tendency to rapid 

 growth ; all the others would long before have been suppressed 



