THE SCIENCE OF PLANT PATHOLOGY. 399 



THE SCIENCE OF PLANT PATHOLOGY. 



By Professor FRANK LINCOLN STEVENS, Ph.D., 



NORTH CAROLINA COLLEGE OF AGRICULTURE. 



TpKOM the time men first had interest in plants, knowledge of 

 -■- their imperfections or premature death has existed, without, 

 however, definite conception that the imperfections in question really 

 constitute a condition of disease. 



The P)ible and the early writings of the Greeks and Eomans con- 

 tain references to what we now recognize as wheat rust, fig blight, 

 insect galls and other of the more strikingly conspicuous plant ailments. 

 Such references are more abundant in the literature of the seventeenth 

 century, and in the latter part of that and the eighteenth century a 

 few papers giving careful descriptions of malformations due to insect 

 invasion appeared. Even the law was invoked to aid in combating 

 the wheat rust in France as early as 1660. Prior to the nineteenth 

 century, however, knowledge of plant diseases can hardly be said to 

 consist of more than mere observation of the fact that such diseases 

 occur, and the little real knowledge that did exist was swamped by 

 rampant superstition. 



It is natural that the first attempts to explain imperfections were 

 founded upon climatic and soil relations. Vestigial beliefs prevail 

 to this day throughout the country among the untutored to the effect 

 that the various blights, rusts, rots, mildews, etc., are caused solely by 

 untoward conditions of weather, or the unpropitious position of celestial 

 bodies or some other occult influence. 



The significance of one great factor in the production of plant dis- 

 ease, namely the parasitic fungi, remained quite unrecognized until the 

 second decade of the nineteenth century. Fungi had been seen upon 

 the plant and had been described in some detail during the preceding 

 decade, but instead of being recognized as causal agents of disease they 

 were, as was the fate of bacteria in the case of animal diseases, by 

 many regarded as products of disease. Before the study of plant 

 diseases could be scientifically undertaken, the basic facts of plant 

 nutrition were to be discovered, the parasitic habit of the fungi proved, 

 the minute anatomy of the plant disclosed. Epoch-making in the 

 disclosure of these desiderata, which may be said to have given birth 

 to plant pathology as a science in the second decade of the nineteenth 

 century were the investigations of the early Dutch, French, German 

 and English botanists. Like bacteriology, plant pathology is an 

 infant science of the last century, owing its being to the perfection of 

 the microscope. 



