SILVICULTURAL SYSTEMS. 25 



more abundantly by giving the crowns more room. 

 Then, when a good crop of seed is likely to appear, a 

 few more trees are removed to give the future seed- 

 lings light enough for healthy growth, but not enough 

 to expose them to danger from frost, drought, or the 

 choking of grass and weeds, for young trees just start- 



FIG. 13. Mixed forest in process of gradual reproduction. Sihlwald, 

 Switzerland. 



ing in life are very sensitive and easily destroyed. 

 Finall} 7 , as the }^oung trees grow taller and stronger, 

 what remains of the old crop is gradually cut away. 

 When it is all gone, usually from ten to twenty years 

 have passed since the reproduction cuttings were 

 begun. 



