MIXED CROP OF UNIFORM AGE. 79 



surface of the soil. The Ougeinia dalbergioides eiijoys this pecu- 

 liarity to a very remarkable extent, as may be observed from the 

 long rope-like roots, which, from being unable to attain organic 

 contact with the soil, even by means of secondary roots, creep 

 along the surface of sheet-rock on hill sides. Such completely ex- 

 posed roots, however, seldom produce suckers, as they become too 

 hard and woody and covered with a thick covering of dead bark 

 imder the unimpeded action of the sun's heat rays, and, being free 

 to develop equally on every side, vigour of growth is too uniformly 

 distributed along their surface. 



XVI. RELATIVE DURATION OF FOLIAGE, AND SEASON OF ITS 

 FALL AND RENEWAL. This condition influences to a very remark- 

 able extent the distribution of many species in a crop. It is evi- 

 dent that, other circumstances being equal, the longer a species re- 

 mains in leaf during the year, the better is it adapted to secure ulti- 

 mate mastery over its companions. A tree in leaf is constantly ready 

 to assimilate new material for its growth, and is either spreading 

 itself out in various directions, or is preparing to do so, the result in 

 either case being that it is able to steal a march on its leafless 

 neighbours, and this with conspicuously greater effect, the earlier 

 it is in renewing its foliage. Thus, where the climate and soil are 

 suited to evergreen species, these always predominate over their 

 deciduous companions. In some parts of Burma evergreen species 

 have invaded the confines of teak, and surrounded in their close 

 embrace isolated trees of that species, which m'ust be the last of 

 their race there, unless equally powerful compensating conditions 

 come to their aid. Again, the sal, which is all but an evergreen, is 

 able to suppress most of its would-be rivals. Thus, in the Raipur 

 district of the Central Provinces, it has encroached on the teak in 

 many places. The Anogeissus pendula is leafless for only a short 

 time in spring, and tolerates few companions of other species. On the 

 other hand, the Boswellia serrata, besides possessing an open crowr, 

 is leafless for from eight to nine months ; so that, although for other 

 and more potent reasons it does grow gregariously, it nevertheless 

 allows other species not only to push up into the leaf-canopy on a 

 level with itself, but also to occupy a permanent and often large 

 place there. Such species are Hardwickia binata, Anogeissus lati- 

 folia, teak, khair, &c., which all retain their foliage for some months 

 after the Boswellia has shed its own, and renew it from several weeks 

 to several months earlier. Indeed, in many localities, the Boswellia, 

 may looked upon only as a temporary natural crop to be replaced 

 later on by more favoured species, to whiqh it is now acting as a 



