152 THE DEVELOPMENT OF BRITISH FORESTRY 



cheaper work than that done in the ordinary way. It 

 is most often profitable where pure crops are grown of 

 a species which produces seed in abundance, and on 

 ground which carries a typical woodland surface flora 

 which does not tend to smother the plants. It is with 

 such species and under such soil conditions that the 

 majority of continental crops are raised, and for these 

 reasons it is possible that the methods practised by 

 continental foresters have been maintained for so long a 

 period in spite of the increasing cost of labour, and the 

 bad results which occasionally follow overcrowding in 

 youth. 



The custom of sowing or planting pure crops goes back 

 to the earliest days of practical forestry. Natural forests 

 are rarely pure, but one species usually predominates, and 

 under favourable conditions produces pure groups of 

 greater or less extent. Beech, spruce, and silver fir are 

 more often found pure than other species on account of 

 their ability to kill out weaker neighbours, and their 

 power of reproducing under thick shade. These pure 

 groups, however, rarely extend over large areas, as 

 differences of soil or situation produce varying conditions 

 which give one species the advantage here and another 

 there. Occasionally one comes across a natural mixture 

 of two species, either of which is able to hold its own 

 against its neighbour, but more often the mixture can 

 only continue when a light-demanding species is found 

 with a slow - growing and subordinate shade - bearer. 

 Another cause of naturally mixed woods is the open order 

 in which the various species often stand, owing to irregu- 

 larity of seeding, or the existence of surface growth which 

 prevents uniform cropping, etc. Hence it happens that 

 the better the soil, and the more varied and stronger the 

 ground flora, the greater the tendency for natural woods 

 to be mixed, while on very poor soils, or those strongly 



