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 spindling 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 foliage. 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 
