Atmospherical Influences 63 
uninitiated, appear as the true source of the disease, are 
merely the result of the unfavorable physiological condi- 
tions of the tree. 
Hence in diagnosing, one should never be satisfied to 
stop short of an examination of the condition of the patient 
in all directions. 
Atmospherical Influences. The conditions of the atmos- 
phere naturally also influence the functions of the tree, but 
are mostly not under control. Here, too, species vary in 
their requirements and in their capacity for adaptation. 
Here even more than with reference to soil conditions (which 
are under control) it is necessary to make sure of the natural 
adaptation of the tree to its surroundings. And, we reit- 
erate, it is not only the species that need consideration, but 
the individual itself, when transplanted from one set of 
conditions to another. For, the individual tree as it grows 
up from the seed has the capacity of adjusting itself to its 
environment, but when suddenly transplanted into other 
surroundings it cannot do so at once. Hence it may be 
ailing for some time until it gradually adjusts itself, or else 
it may succumb to the unaccustomed conditions, either 
directly or by physiological disease, or indirectly by falling 
a prey to parasites in its enfeebled state. 
If, in planting, species or specimens have been chosen 
which are adapted neither to the conditions of humidity or 
drouth, nor to the temperature changes of the atmosphere 
common in their new home, they will suffer, and perhaps 
die, and should be replaced by those which are better suited 
to the environment. ‘Theoretically, it may be possible to 
help such exotics by regulating the soil conditions, and to 
mitigate climatic conditions by screens and other protec- 
tion; but practically this is usually too troublesome. 
Soil and atmosphere are in such interdependence as far 
