CHAPTER XXXVI 

 NON-PARASITIG, OR PHYSIOLOGIC PLANT DISEASES 



The non-parasitic diseases of plants traceable to the unfavorable 

 conditions of the slope, physical and chemical character of the soil in- 

 cluding the deficiency or excess of water content, as well as the unfavor- 

 able climatic influences, have been discussed at length by Sorauer in 

 his "Handbuch der Pfianzenkrankheiten'' (3d Edition, assisted by 

 Lindau and Reh, 1908) and the English translation of the 3d edition 

 of this book by Frances Dorrance under title of "Manual of Plant 

 Diseases," issued in parts. Four parts have already appeared on Non- 

 parasitic Diseases. At length also are considered the poisonous in- 

 fluence of gases and other chemicals together with wound and gall 

 diseases. Gummosis and several other physiologic diseases have been 

 described by him. A general treatment of these diseases has been 

 made in Part II of this book and, therefore, such general considera- 

 tions need not be rehearsed here. A few specific cases will be given 

 by way of introducing the student to another phase of phytopatho- 

 logic work.^ 



It should be stated at the beginning that no sharp line can be drawn 

 between parasitic and non-parasitic diseases. If they were controlled 

 by a single set of factors this might be done, but complications always 

 are involved. 



The classification, however, is a convenient one and we can, there- 

 fore, use the terms physiologic and non-parasitic merely as conventional 

 designations for a certain class of diseases. A convenient bibUography 

 of non-parasitic diseases of plants by Cyrus W. Lantz forms part of 

 Circular No. 183 Agricultural Experiment Station, University of Illinois, 

 Urbana, May, 1915. The following are some of the names applied to 

 such diseases in the original papers listed in the above-mentioned 

 circular by Lantz: Anaheim, Bitter-pit, Brunissure, Brusone, Chloro- 



' Smith, R. E.. The Investigation of Physiological Plant Diseases. Phyto- 

 pathology, V, 83-93, Apr., 1915. 



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