1 86 Studies in Forestry [CHAP. ix. 



(i) predominating, (2) dominant ', (3) dominated \ and (4) sup- 

 pressed. 



As, during the gradual process of death and decay that 

 takes place when stems become suppressed, certain physio- 

 logical conditions obtain, which are extremely favourable to the 

 breeding of insect enemies and the propagation of fungoid 

 diseases, this class of individual stems should invariably be 

 removed during thinning operations. By this means a freer 

 circulation of air and a better utilization of the soil-nutrients 

 are also at the same time effected. 



To what extent a simultaneous removal of the dominated 

 class should proceed, depends in each case on the concrete 

 factors of soil, situation, species of tree, age of crop, mode of 

 treatment, &c. If the struggle were left to nature unassisted 

 it would be carried out most rapidly on fertile soils ; but, on 

 soils of merely average or inferior quality, it would be so much 

 prolonged in the case of shade-bearing species of trees as to 

 result in overcrowding of the crop throughout the pole-forest 

 and the young tree-forest stages of growth. 



From the sylvicultural point of view, however, the main 

 objects of care are the timber-trees which it is desired to 

 utilize on their attaining full financial maturity ; and any 

 measures that will aid in stimulating them to the speedy attain- 

 ment of large remunerative dimensions must deserve favour- 

 able consideration. Year by year the number of individual 

 stems, from which it is possible that the future mature crop 

 may be formed, becomes diminished ; and the removal and 

 the utilization of all unnecessary stems are not only a means 

 of improving the growth of the predominating and dominant 

 portions of the crop, but are likewise a source of revenue, 

 which should be realized as soon as available, in order to 

 reduce the capital cost of the crop both at present and up to 

 its final clearance. And these preliminary or intermediate 

 returns are often of no mean value where any good market exists 

 for small timber like poles and pit-props. Thus Grebe, a dis- 



