Practical Sylviculture 99 



species. There are other limitations that largely govern 

 the suitability of localities for growing certain trees, the 

 chief of which are soil and moisture. 



Soil and moisture. — The amount of moisture and the 

 quality of the soil, both chemical and physical, frequently 

 determine very largely the local tree growth. For ex- 

 ample, the white pine is excluded from many areas well 

 within its range on account of excessive moisture or the 

 total lack of clay in the soil, while the tamarack, which 

 has much the same range, is found in ; pure stands in the 

 low swampy places, and even in mixture with the pine. A 

 white pine planted in a swamp, or a tamarack on a dry 

 hillside, would not do well even in the center of their 

 range. Only when the climate and soil moisture are 

 favorable, as indicated by the conditions of natural growth, 

 can the success of any forest growth be assured. The 

 exceptions to this rule in the case of individual trees will 

 be considered under ornamental planting. 



Selection of seed. — All seed for sowing should be 

 cared for and tested as described in the "farm nursery" 

 (page 112). The quality of the seed for broadcast sowing is 

 even more important than for seed-bed sowing, because 

 it is likely to lie on the ground a much longer time before 

 germination takes place. Moreover, the seed sown 

 broadcast lies on the surface of a poorly prepared soil 

 which the roots have to penetrate to obtain a footing. 

 Only the vigorous-growing seeds can overcome this 

 obstacle, and even many of them exhaust their vitality 

 and die before they can establish a root system. 



Soil cover. — Practically every location in which seed- 

 ing is under consideration will have a soil cover that 



