22 ELEMENTARY FORESTRY. 



other shade enduring. The words tolerant and intol- 

 erant are also used as distinguishing the peculiarity of trees in 

 this respect, and they are perhaps better terms. Trees that are 

 known as tolerant generally have a thicker mass of foliage 

 than those that are intolerant of shade. This simply means 

 that their lower leaves can withstand the shade of their upper 

 leaves. While it is not an absolute rule that tolerant species 

 have a thick mass of foliage and intolerant trees open foliage, 

 yet it is so generally true that where the characteristics of a 

 tree are known it serves as a very reliable indication. Most 

 trees are much more tolerant of shade when young than when 

 old. Among our tolerant trees may be mentioned the Spruce, 

 Oak, Balsam, White Cedar, Red Cedar, Hornbeam and Hard 

 Maple. Among our intolerant species are Poplars, Cotton- 

 wood, Willows, Soft Maple and Birch. Of our native pines, 

 the White Pine is much more tolerant than either the Jack or 

 the Norway Pine, which are quite intolerant of shade and soon 

 succumb if they are protected from the full sunlight. 



Trees Protect One Another and are Mutually Helpful, 

 and many trees that are quite hardy on the limits of their 

 growth when grown in groups, will fail if grown singly, as for 

 instance the Hard Maple in exposed parts of Minnesota. Trees 

 also interfere with one another and struggle for light and soil 

 conditions, and the weaker trees are destroyed. So true is this 

 that where the land is thickly seeded with even-aged trees, they 

 may all become weak and sickly because of hindering one 

 another. On the other hand, this crowding of trees forces them 

 to take on an upward growth and kills out the. lower branches. 

 Trees growing under such conditions make long timber free 

 from knots, which is therefore most valuable. 



SOIL CONDITIONS. 



Water Supply. Water is the most important element in 

 soils for tree growth, and the greatest attention must be .uiven 

 to its conservation and distribution through the soil. Trees 

 do not grow to best advantage in very wet or in very dry soil, 

 although some can live and almost thrive under such unfavora- 

 ble conditions. There is very little land, except in the arid 



