63 



by the soil and locality, the course of development of the crop by 

 the treatment and system of working. Of the course of growth in 

 crops worked by the j-.irdinage and coppice methofls but little is as 

 yet known, but a flood of light has been thrown on the growth of 

 regular crops treated by the uniform method by the labours of the 

 German Department for Forest Research. The remarks which 

 follow refer only to such crops. 



A. Natural coDFtitntion of s:eu]*-classe6. 



In every crop we can recognise, besides the over-topping and 

 dominant individual, two lower classes of dominated and over- 

 topped ones, and, if no thinning have been made, also a fifth class 

 of suppressed stems. The first two classes form what mav be 

 called the main crop, the other three the subordinate crop. It is 

 obvious that in the ordinary course of development of the crop 

 fresh stems are constantly passing into the lower classes from the 

 immediately upper ones, and from the main crop into the subordi- 

 nate one, from which they are ultimately removed by thinnings or 

 natural decay and death. The result is a constant diminution of 

 the number of stems composing the main crop. 



The original number of individuals in a crop de])ends on the 

 manner of its constitution, according as it has sprung up from 

 self-sown seedlings or from artificial sowing (generally executed 

 close), or from transplants (generally put out comparatively far 

 apart). The number of stems diminishes rapidly in youth, less 

 rapidly in middle age, and still more slowly in old age ; rapidly in 

 favourable soils and localities ; slowly, but steadily, up to a great age 

 in unfavourable places. At one and the same age more stems stand 

 in unfavourable soils and localities than in those more suitable. 

 A crop of Scotch pine of the best quality contains 1,200 stems per 

 acre at 30 years of age, but only 140 stems 90 years later at the 

 age of 120 years. 



This constant and great diminution in the number of component 

 individuals results in a considerable falling off of the increment, 

 the consequence being that both the current and mean annual in- 

 crements reach their culminating point earlier in the case of the 

 crop than in that of the individual belonging to the dominant or 

 representative class. 



Since thinnings ai.d decay and death remove mostly the indivi- 



