SHADE TREES. 



215 



more injurious than a loose-textured soil would have been. In this case 



the death of the trees was caused by too close contact of the soil with 



the bark. When a stone 



wall is first built around the 



tree at sufficient distance to 



allow for future growth, to 



keep the soil away from the 



trunk, trees filled in to a 



height of 5 or 6 feet have 



been known to survive for 



many years. 



Some trees are undoubt- 

 edly more easily injured by 



earth fillings than others, 



but building a wall around 



them to keep the dirt from 



the trunk, or even the use 



of cobble stones, brick or 



coarse gravel close to the 



trunk, tends to prevent in- 

 jury. Banking soil for even a few inches around young trees sometimes 



causes injury. 



There are many instances where trees which have been buried partly 



up the trunk threw out a new root system nearer the surface of the soil. 



The tree shown in Fig. 87 had been filled 

 in with soil to a depth of 4 feet thirty-five 

 years ago, and in removing the tree it was 

 found that the old stump and roots were 

 all decayed, but the new surface roots had 

 proved sufficient to support the tree. 



Fni. 88. — Red maple injured by earth lilling 

 foot deep. 



Bleeding of Trees. 

 A great many trees sufter from bleeding 

 from different types of injury such as borers, 

 lightning strokes, frost cracks, splitting of 

 the trunk, and occasionally Hnemen's spurs. 

 Often trees filled with cement bleed; and 

 the exudation, containing magnesium com- 

 pounds derived from the cement together 

 with various microorganisms which thrive 

 in the exuded sap, gives an unsightly 

 appearance to the bark. Bleeding to ex- 

 cess is very injurious. Sometimes the death of trees from this cause is 

 sudden, and in other cases the tree will linger, gradually dying back at 

 the top, and eventually dying. The exuded sap, or "slime-flux," some- 

 times proves detrimental to the living tissue, as shown by the presence 

 of saprophytic fungi. 



Fio. 89. — Wall built around the 

 base of a tree to prevent in- 

 jury from earth filling. (See 

 Fig. 88.) 



