Effect of Soil Conditions 6i 



more readily than others. These latter, like the Swamp Oak, 

 Bald Cypress and Alder, especially when they have once 

 adapted themselves to swampy life are at a great disadvan- 

 tage if the conditions are suddenly changed. It is, there- 

 fore, possible that in newly planted trees any ailment is 

 merely due to change from one set of conditions to another, 

 to which the tree is not as yet adapted. Thus a tree moved 

 from a shady position to one of more intense hght will suffer 

 for a time until the fohage is adapted to the new environ- 

 ment. 



In passing it is interesting to note that even a physically 

 moist or wet soil may be physiologically dry, that is to say, 

 the water may not be available to the rootlets. This is 

 the case in swamps where the water is saturated with humic 

 acids from the decay of vegetable matter, these acids having 

 a greater attraction for the water than the rootlets can exer- 

 cise. Here we see quite frequently the disease called slag- 

 head, which consists in the drying of the top due to deficient 

 water-supply at the root. 



It is, therefore, necessary to be cautious in the attempt to 

 diagnose and correct water conditions. 



The death of the top, top dryness or slag head, is gradual, 

 the lower branches remaining green, their annual shoots, 

 however, becoming shorter. It is a result of drouthy con- 

 ditions at the root, which may be caused in various ways, 

 other than the one just cited. In forests and parks, by cut- 

 ting out or burning the undergrowth and by severe trim- 

 ming, the sun is given access to the ground. As a consequence 

 the decomposition of the litter and humus which covers 

 the soil proceeds more rapidly, while at the same time on- 

 account of the increased light supply the fohage becomes 

 more active. Stimulated by the increased food elaboration, 

 ail the benefited trees at first grow more vigorously and their 



