78 EXPERIMENT STATION. [Jan. 



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 G feet have 

 been known to survive for many years. 



Some trees are undoubtedly more easily injured by earth fill- 

 ings 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 injury. Bank- 

 ing soil for even a few inches around young trees sometimes 

 causes injury. In the case of a youug orchard which we ob- 

 served a few years ago soil was piled up 3 or 4 inches around 

 the trunks of some of the trees for the purpose of protection, 

 but in nearly all instances the tissue underneath was dead, while 

 the trees not treated in this way were all alive. 



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. 8 had been filled in 

 with soil to a depth of 4 feet thirty-five years ago, and in re- 

 moving 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. 



Exposure of Eoots. 



Occasional injury occurs to the large roots of trees from re- 

 ffradinir and other causes. A few vears ao-o we had occasion to 

 examine a large number of hickory trees (Canja aiha) located 

 on a country estate which had been injured quite seriously, 

 apparently from sun scald. They had been growing for many 

 years under natural conditions and were fairly vigorous, but 

 during the construction of a large house, and the regrading of 

 the ground, many of the roots — particularly the buttresses — 

 had become exposed. In every case where the soil was taken 

 from the base of the tree and the roots wove exposed, the tissue 

 was all sun scalded, but the tissue on the underside of these 

 roots was perfectly normal. In some cases this caused the death 

 of the trees. 



It is sometimes possible to expose the larger roots of trees 

 without doing any harm, but at other times sun scald will 



