242 SYLVICULTURE IX THE TROPICS pt. 



hi 



rotation of which starts at A with the seed -fellings. 

 During the first period of its existence (A to B) the 



after-fellings are being made, 

 while during the next (B to 

 C) the area is gone over with 

 cleanings. Next come re- 

 peated thinnings during the 

 periods C to D, D to D l5 

 Dj to D 2 , and so on to E, 

 at first at short intervals, 

 then more protracted, until, 

 during the last period of the 

 rotation (E to A), the pre- 

 FlG 83 paratory-fellings are carried 



out. 

 In a mixed crop the different species may be found 

 in groups, in which case each separate group may be 

 treated like a pure crop ; or, as is more usually the case, 

 the mixture may exist, probably in varying proportions, 

 all over the area to be treated. In this case the care of 

 the forester must be devoted to encourage a proper and 

 sufficient proportion of the more valuable species, and 

 thus it will not necessarily be the strongest individuals 

 that will be helped along, but, where inferior species 

 tend to crowd out the more valuable ones, they will 

 have to make way for them until the proper proportion 

 of different species has been obtained. If the valuable 

 species are the faster growing, and are shade-avoiding, 

 they will soon form an upper tier or story, the other 

 species protecting their boles and the soil below their 

 open crowns. Thus, to take an example from Ceylon 

 forests, under an upper tier of Mimusops hexandra and 

 satin wood [Chloroxylon Swietenia) will be found a 

 lower one of shade-enduring species such as Nephclium 

 Longana, Sapindus emarginata, HemicycJia sepiaria; 

 while ebony {Diospyros Kbenum), which is also shade- 

 enduring, will work its way into the upper tier, but 

 more slowly. It will thus frequently happen that, in a 

 mixed crop, after the full growth in height of the 



