230 SYLVICULTURE IN THE TROPICS rx.ni 



the neighbouring crowns close over them, they pass from 

 the dominated to the suppressed stage, and sooner or 

 later, according to whether they belong to shade-endur- 

 ing species or not, they cease to be capable of assimilat- 

 ing food and they die, leaving their betters to fight it 

 out among themselves as to which will ultimately remain 

 victors. A variety of causes may lead to the victory 

 or defeat of the individuals composing the crop. Just 

 as among men and other animals some have a greater 

 inherent strength than others, among the plants some 

 are stronger than others ; and there may be other factors 

 which may also incline the balance in favour of one or 

 the other, such as variations in the quality of the soil, 

 or attacks by insect or vegetable enemies, such as plant 

 parasites, climbers, etc. 



With coppice- shoots of the same age and species 

 there is a similar struggle, only it usually starts earlier, 

 for coppice-shoots at first usually grow quicker than 

 seedlings, and when the crop consists partly of coppice- 

 shoots and partly of seedlings, if the latter are not 

 shade-enduring they will soon be passed and killed by 

 the former in the struggle for light and air. 



The conditions in a crop composed of coppice-shoots 

 and of seedlings of the same age are somewhat similar 

 to those which exist in a crop of seedlings, or of seed- 

 lings and coppice-shoots of the same age but of different 

 species. 



Here the struggle for existence may become very 

 complicated. Not only do the individuals of each species 

 vary among themselves in their rate of upward growth, 

 but there may be a still greater variation in the rates of 

 growth between the component species. Again, among 

 the slower growing, there may be some which are very 

 shade-enduring, and which may ultimately win their way 

 into the upper tier, while among those which started 

 well in the race there may be some which do not grow 

 of a great size, or which are not long lived ; or it may be 

 Hint parasites, climbers, or atmospheric conditions may 

 cripple some more than others. It is thus difficult to 



