24 ELEMENTS OF SYLVICULTURE. 



CHAPTEK I. 



METHOD OF THINNINGS. 



NATURAL PHENOMENA ON WHICH THE METHOD is 

 FOUNDED. 1st. In order that a seed may germinate, 

 air and a certain quantity of heat and moisture must 

 be present. These three elements acting simultan- 

 eously are necessary and sufficient. Light is useful, 

 but it is not absolutely necessary, and the heat that ac- 

 companies it, if too strong, as is often the case, may 

 cause the seed to dry up, and thus prevent germination. 



Nor again is the presence of soil essential to ger- 

 mination, though it favours it in so far as it distributes 

 to the seeds in suitable proportions the elements 

 of which they stand in need. But for this purpose 

 the soil must be sufficiently free, and rich enough to 

 provide nourishment for the plants immediately after 

 germination. 



As long as the soil is not well protected by the 

 young plants, and their rootlets are small and have 

 not penetrated deeper than the topsoil, which may 

 dry up, the young plants require shelter from the 

 heat. Later on they require complete exposure to 

 the action of sunlight, and they should be gradually 

 brought under its influence. 



If to these facts, which are a matter of observation, 

 we add the necessity of obtaining a thorough re-stock- 

 ing of the forest, we deduce the following conditions, 

 bearing upon natural reproduction and growth dur- 

 ing the early years : 



A free and rich soil. 



