70 Stkvkns — Science of Plant Pathology. [June 



meats of life, viz., health, sickness and death. A healthy 

 soil may, from an agricultural point of view, be regarded as 

 one capable of fulfilling all its vital functions; a sick soil, one 

 in which some functions are impaired. Of only one class of 

 soil sickness may I speak, namely, that which results in pro- 

 ducing sick plants by harboring pathogenic germs. The cot- 

 ton wilt, the Texas root rot, the watermelon, tobacco, tomato 

 and cabbage wilts, the cabbage club foot and the onion smut 

 are conspicuous examples of diseases so propagated. Dis- 

 eases of this type not only destroy the crop, but they preclude 

 the possibility of successful culture of the plant in question, 

 or of its close botanical relatives for many years. Such foes 

 to agriculture have completely destroyed the possibility of 

 tobacco growing on many farms otherwise eminently adapted 

 to this crop and ill adapted to any other, resulting in great 

 depreciation in the value of the land. This encroachment 

 upon valuable soil will proceed yearly, and with geometrically 

 increasing rapidity, until means of prevention are discovered, 

 as they have now been in some instances, and the method of 

 prevention becomes common knowledge. Soil diseases, the 

 most dreaded of all dangers to the plant, are prevalent to 

 much greater extent in the south than in the north. One 

 field is known to exist in South Carolina upon which neither 

 melons, cotton nor cow-peas can be grown. It is conceivable 

 that many other germs could infest one and the same field, 

 but no greater affliction concerning such staple crops seems 

 possible. 



Growth in popular appreciation of the importance of plant 

 diseases and of the value of remedial and prophylactic meas- 

 ures is perhaps the most striking characteristic of plant path- 

 ology in the last twenty years. At the beginning of this per- 

 iod spraying was in no wise general. It was of rare occur- 

 rence. Man suffered unresistingly the attacks of the molds, 

 mildews, rots and blights. The circulation of thousands of 

 state experiment station bulletins and similar bulletins from 



