58 Diagnosing of Diseases 



place, until in an unfavorable season this reduction of 

 water and air becomes fatal. 



Moreover, as the root system expands it enters new regions 

 and possibly less favorable strata than it occupied before. 

 Therefore, whenever direct visible causes are absent, an 

 examination of the soil conditions, especially those of water 

 supply and aeration, furnishes in most cases the basis for 

 the diagnosis of disease. Excess or deficiency of water, 

 and deficiency of air at the root produce very similar results 

 in the appearance of the tree above ground. 



Pale or yellowish foliage, undersized leaves, short annual 

 shoots, or long spindhng ones poorly foliaged, and finally 

 the dying of branch tips are the results of a compact heavy 

 soil. Especially is this true in a cool wet season, when, 

 owing to the excess of water in the soil, air (or oxygen) is 

 excluded from the roots, and their respiration rendered 

 imperfect. 



In newly planted trees, especially in compact soils, these 

 same symptoms, followed by death, often appear as a 

 consequence of too deep planting. The aeration of the roots 

 and lower portions of the tree being thereby precluded, 

 alcoholic fermentation of the cells sets in, and the water- 

 conducting function of the cambium and young wood is 

 impeded, as becomes evident from the sickly yellow appear- 

 ance of the foHage. If the soil is not corrected, in a year or 

 in a few years the tree succumbs. Some species, however, 

 such as willows, poplars, elms, and basswood, may under 

 these conditions form new superficial roots from the bole 

 and thus help themselves. 



A surplus of water in the soil, besides unfavorably influenc- 

 ing aeration and thereby producing the symptoms mentioned, 

 may also produce a kind of dropsy, if weather conditions 

 are favorable to rapid transpiration or if light conditions in 



