270 A MANUAL OF FORESTRY. 



per cent, of it germinate. One pound of clean seed 

 contains something like 800,000 seeds. 



Direct sowing is rarely done. Broadcast sowings 

 would require about 30 pounds of seed per acre, which 

 should be very thinly covered, only about one-eighth of 

 an inch. The seed germinates after 2 to 3 weeks. Seed 

 which has ripened early in the autumn may germinate 

 in the same year ; otherwise it lies dormant till spring. 



In nurseries the seed is sown broadcast and covered 

 by sprinkling a little earth over it. The one-year-old 

 seedlings may be pricked out and left for one or two 

 years in the nursery lines, according to requirements. 

 On the continent one or two-year-old plants are used for 

 planting. 



Birch can easily be regenerated naturally under a 

 very small number of mother trees. Generally it 

 appears where it has a chance of springing up, and the 

 forester has more to fight against it than to favour it. 



i. Tending. 



Fertility of Soil. Early opening out and a thin crown 

 do not enable the Birch to act beneficially upon the soil ; 

 hence it should not be grown pure, except on localities 

 where more valuable trees will not thrive. 



External Dangers. Birch being very hardy, requires 

 no tending against climatic influences ; the damage done 

 by snow, rime, and storms, is moderate. It is less 

 nibbled by cattle and deer than almost any other broad- 

 leaved tree. It is attacked by mistletoe. 



Insects. The leaves support a very large number of 

 larvae, which, as a rule, are not gregarious. Injury is 



