DIEECT SOWINGS. 245 



germinate only in the second spring,, and produce 

 sickly plants without any promise. Silver fir seeds 

 cannot be kept beyond one winter. 



NOTE. It is obvious that direct sowing can be 

 resorted to only with hardy species : those of a 

 delicate constitution can only be sown where suffi- 

 cient protection exists, for instance, under standing 

 timber which has been thinned out to the extent 

 required by the primary cutting. This is done when 

 one species is to be substituted for another or a 

 mixture restored which has been destroyed. But it 

 is quite impracticable on perfectly bare wastes. To 

 remedy this defect several methods have been pro- 

 posed, such for instance, as a previous crop of trees 

 of rapid growth, or the simultaneous sowing of 

 cereals. This latter plan is good for species which 

 require nursing for only a limited period, like the 

 elm for example, which germinates in warm weather ; 

 but it would never do for species which require 

 shelter during several years. For these a previous 

 timber crop is necessary, and as the cost of labour 

 is the same in each case preference ought obviously 

 to be given to trees capable of covering the outlay 

 within a definite period. The Scotch pine, the birch, 

 and, in strongly calcareous soil, the black Austrian 

 pine seem to fulfil best this condition. The first 

 two especially possess light foliage, and experience 

 proves that when they attain the dimensions of poles, 

 the shelter of their crowns is very favourable for the 

 introduction of the oak, the beech, and the silver fir 

 under them. The oak, it is true, is not averse either 

 to light or heat, but it is very sensitive to late frosts ; 



