THE KUHNIAN PERIOD 45 



three great scientists. None of them were plant pathol- 

 ogists, though all made investigations and discoveries 

 not only epoch making in their respective fields, but fun- 

 damental to related sciences and to none more than phyto- 

 pathology. I refer to the great German botanist and 

 mycologist, Anton de Bary, who lived and worked from 

 1831 to 1888; the equally noted chemist, Justus Freiherr 

 von Liebig, 1803-73, the father of agricultural chemistry; 

 and the famous French chemist and bacteriologist, Louis 

 Pasteur, 1822-95. 



The opening of this period is marked by the publica- 

 tion in 1853 of that classical work of de Bary's, Die Brand 

 Pilze, in which the young investigator (then twenty-two 

 years old) established beyond doubt the causal nature of 

 the fungi found associated with rust and smut diseases. 

 In 186P he published his investigation on the cause and 

 nature of the late blight of potatoes in which he proved 

 the causal relation of Phytophthora infestans. In 1865^ 

 he published his work, establishing the relation of the 

 aecidium on barberry to the rust fungus on wheat. These 

 are but a few of the striking pieces of work of an almost 

 endless number of similar investigations on the nature of 

 the relation of fungi to different diseases. One should 

 read the list of his contributions in the Lindau and 

 Sydow Thesaurus, Vol. I. 



Heinrich Anton de Bary was born at Frankfurt-am- 

 Main. He became interested in botany while still in the 



' de Bary, A. : Die gegenwartig herrschende Kartoffelkrankheit, ihre 

 Ursache and ihre Verhiitung, pp. 1-75, Leipzig, 1861. 



■•"de Bary, A.: Neue Untersuchungen iiber die Uredineen, insbeson- 

 dere die Entwiclcelung der Puccinia graminis und den Zusammenhang 

 derselben mit Aecidium Berberidis, Monatsber. d. Kon. Preuss. Akad. 

 der Wiss. aus dem Jahre 186S : 15-50, Berlin, 1866. 



