160 Studies in Forestry [CHAP. vin. 



fully to utilize its nutrient soluble salts. It also happens that 

 the favourable admixture of a certain mineral element in the 

 soil affords special advantages to particular classes of trees 

 as, for instance, the better growth of Beech, Maples, Ash, and 

 Black Pines on soils that are of a limy composition. And, 

 in a certain degree connected with the conditions as to atmo- 

 spheric humidity and soil-moisture, danger from late frosts in 

 spring, or from early frosts in the autumn, can be so great as 

 to preclude the planting out of Oak, Beech, Ash, Silver Fir, 

 and even Spruce without a certain admixture of quick-growing 

 softwoods as protective growth and nurses. Again, where 

 heavy falls of snow are apt to occur, the brittle Scots Pine 

 is less able to support the masses of snow and ice accumu- 

 lating on its loose crown than other more elastic evergreen 

 conifers. 



And when one comes to the practical question, not only as 

 regards the suitability of soil and situation for any given 

 genus, but also with respect to their suitability for one particular 

 species above all others, or with a view to the selection of the 

 best genera for the formation of mixed crops, which have 

 invaluable advantages over pure crops (see Chapter VI), the 

 difficulties connected with the choice become increased. Thus 

 the cultivation of the pedunculate Oak, Larch, Spruce, and 

 Silver Fir will only prove satisfactory on soils and situations in 

 every respect suited to their normal requirements. But over 

 every large woodland tract there are variations, in quality of soil 

 and degree of soil-moisture, which must be carefully observed 

 and taken advantage of in the formation of mixed crops, instead 

 of attempting to carry out the mixture in anything like a rigid 

 or stencilled manner. No better example of want of prudent 

 consideration, or want of knowledge, of the natural requirements 

 of any species of forest tree can be given than to point to the 

 mistakes made in the latter half of last century and the begin- 

 ning of the present with respect to the extensive introduction 

 of the Larch into Scotland. These errors have only had 



