BRITISH FOREST TREES 199 



growing-space, uncertainty about the development of the pre- 

 dominating stems, and long-continued individual struggle 

 for the supremacy, all militate so much against the ultimate 

 returns derivable from the mature crop that, in the case of 

 oak, thinnings must be carried further than with the beech, 

 and should include all individuals that can be spared from the 

 canopy, as, even where petty interruptions are thus made, 

 the blanks soon close up again. Thin early and often is the 

 golden rule in the tending of the oak, and in the frequent 

 removal of indifferent individuals lies the best means of 

 permanently retaining a good canopy ; by this means the 

 best mature crop is not alone assured, but also the advantages 

 of early and sometimes good returns in the meantime. 



Pure forests of oak are more usually the outcome of grow- 

 ing or planting than of natural reproduction, and they exhibit 

 differences of growth, especially in the more advanced stages 

 of development, varying with the qualities of soil over which 

 they are found. Where not hindered by strong growth of 

 grass, the young plants rapidly shoot ahead of the dangers 

 most common to the youngest period ofdevelopment, but from 

 then till about the eighth to tenth year they tend more towards 

 lateral than to upward growth. Shortly after forming close 

 canopy, however, the young thicket begins to clear itself from 

 branches, to confine the foliage to the upper portion, and to 

 enter upon the struggle for individual existence shown in 

 vigorous growth in height. On deep, fresh soil in mild locali- 

 ties this culminates about the thirtieth to fortieth year of 

 age, but on less favourable soils and situations not till ten 

 to fifteen years later if the density of canopy has been main- 

 tained, which is not always the case as, except on fresh 

 fertile soils, there is often a tendency towards interruption 

 of canopy throughout the earlier part of the pole-forest 

 stage of growth, in consequence of insufficient light and 

 growing-space. With the efforts of the survivors to extend 



