DETAILED EXPOSITION. 



SECTION I. 

 DISEASES DUE TO UNFAVORABLE SOIL CONDITIONS. 



CHAPTER I. 

 THE LOCATION OF THE SOIL. 



Even if the diseases which are due to an unfavorable location of culti- 

 vated land are better understood by means of the different factors because of 

 which this position becomes injurious to plant growth, we have still con- 

 sidered it necessary to describe in the following section the general conditions 

 due to different locations. We have done so because it is of special impor- 

 tance to the guiding principle of this manual and to any reference to a pre- 

 disposition to certain diseases which is developed from this location of the 

 soil that it be shown how the material and formal structure of any plant 

 species changes with the condtions of the habitat, how thereby separate func- 

 tions may sometimes be suppressed, sometimes advanced, and how accord- 

 ingly the different localities impress their definite characteristics on the plants 

 which, on this account,, must behave very differently in relation to the differ- 

 ent injurious causes. 



I. ELEVATION ABOVE SEA LEVEL. 



a. General Changes in Habitat in Relation to Herbaceous Plants. 



There is no need of discussing further the fact that the temperature al- 

 ways falls with an increase in elevation of any cultivated surface above sea 

 level and that this fall in temperature is a determining factor for limiting 

 vegetation, on which account the time of harvest in mountains must always 

 be later than on lower levels. It is an universally recognized fact that this 

 later harvest brings with it great difficulties in curing the grain and not in- 

 frequently makes necessary special precautions in high mountains, and that 

 despite these precautions there often takes place a blackening of the grain as 

 a result of the beginning of fungous growth. An example with exact figures 



