137 



imity, — or, on the other hand, the forest may make streaks across the field 

 accessible to rains and prevent the rapid drying off of the seeds. In the first 

 case, the forest may become a harboring place for injurious insects. It has 

 often been observed in the case of dwarf cicades that they begin their de- 

 vastation of the fields from the dry edges of the forest. The more severe 

 attacks of Puccinia, Ophiobolus and Leptosphaeria herpotrichoides serve as 

 examples of the influence of moisture, near the border of the forest, upon 

 fungous diseases. Goethe's discoveries^ as to the influence of the place of 

 growth upon the canker of fruit trees, caused by Nectria ditissima, must 

 be considered. The tendency to disease from canker is favored by an in- 

 creased humidity as offered by higher regions or also by cold valley soils. 

 "The trees show in such places a meagre growth and are covered with 

 mosses and lichens. Similar conditions are observed also near extensive 

 forests, out of which cold, damp air streams even in the summer." 



Goethe, Rudolph, Ueber den Krebs der Obstbaume. Berlin 1904. Paul Parey. 



