256 BIEECT SOWING. 



(iv) The requirements of those species in respect of light. 

 Some species acquire their most useful shape and dimensions in 

 more or less open leaf-canopy, others only on condition that the 

 leaf-canopy is more or less complete, and so on. 



(v) The craving of those species for the early formation of a 

 leaf-canopy, in order to be able, thanks to the mutual protection 

 that trees standing together afford each other, to start up vigor- 

 ously. 



(vi) The necessity for an early suppression of the weeds and 

 other noxious vegetation present. Such vegetation may be harm- 

 ful either on account of the rapid and invasive spread of their 

 crowns or roots or rhizomes, or on account of the tall and dense 

 growth they form, or of the ease and rapidity with which they 

 multiply by means of seed or suckers. 



(vii) The object to be secured by the sowing. This object may 

 be very various. For instance, a certain species may be absent or 

 insuflSciently represented, and it is desired to introduce it or to 

 increase its proportion. Or, again, it may be decided to renew 

 or to maintain in undiminished vigour a copse, that is exploited 

 before any of its component individuals can become fertile and 

 produce self-sown seedlings, or which is composed of a species that 

 caUnot reproduce itself naturally from seed under the given local 

 conditions. Or again, it may be necessary in some open situations 

 to raise a mere nurse, and therefore temporary, crop of some hardy 

 and quick-growing species, in order afterwards to be able to intro- 

 duce under its shelter the species which are to compose the forest 

 permanently, but for young individuals of which the prevaiHng 

 local conditions are unfavourable. And so on. 



(viii) The difficulty of securing success. The more casualties 

 we anticipate, the larger must be the aggregate area actually sown 

 and consequently the narrower the uncultivated intervals. 



(ix) The amount and effectiveness of the supervision available. 

 The less the Supervision and the more untrustworthy the people 

 exercising it, the closer together must the strips lie. 



(x) On the"^amount of labour that may be available or consi- 

 dered desirable to devote to the repair of failures. 



When the area to be sown already contains a more or less open 

 forest growth sufficiently promising to be utilised, the distance 

 between the strips will rarely be less than 10 feet, the maximum 

 being about 50 feet, but the average as low as 20 feet. The inter- 

 vals may be still wider if a new species has to be introduced in an 

 alf eady existing forest, and a fortiori if it is proposed merely to 



