154 PLANT PATHOLOGY 



the leader. In 1853 he published his investigations on the rust fungi 

 and the diseases caused by them, with special reference to the 

 cereals and other useful plants; and in 1865 he gave to the world 

 the first demonstration of hetercecism among the Uredinales. 



Nothing could better show the unprejudiced attitude and clear 

 judgment, together with facility for turning unintentional sugges- 

 tions to account, which De Bary displayed in his studies, than this 

 demonstration of hetercecism. For nearly a century English and 

 Dutch farmers had been convinced from observation that the cup- 

 fungus on barberry bushes in some manner promoted, or possibly 

 gave rise to, the very unlike wheat-rust. These two forms of fungi 

 are so dissimilar in appearance and structure that professional 

 botanists would not entertain the notion that they were but two 

 forms of the same species. Nearly at the beginning of the century, 

 and more than fifty years before De Bary began his experiments, 

 Sir Humphry Davy, the greatest chemist of his times, and well 

 versed in the natural sciences, said: "The popular notion among 

 farmers, that a barberry tree in the neighborhood of a field of wheat 

 often produces the mildew [English term for rust], deserves exam- 

 ination. This tree is frequently covered with a fungus, which, if it 

 should be shown to be capable of degenerating into the wheat 

 fungus, would offer an easy explanation of the effect." 1 Others 

 before and after Davy recorded similar opinions. After De Bary 

 had shown by sowing spores of wheat-rust on barberry leaves, and 

 raising the cup-fungus, that the views of the English farmer were 

 well grounded, Continental botanists made many additional studies 

 of hetero?cious rusts, and in 1880 Professor Farlow started the work 

 in America. But in Great Britain, where the annual field demon- 

 stration was so plain as to attract the attention of the unlettered, 

 De Bary's results were discredited for more than a quarter of a 

 century, and almost the only work in heteroecism so far done, 

 unless we include the recent brilliant work of Marshall Ward and 

 his pupils on the transference of the uredo-stage to allied hosts, was 

 accomplished in the decade following 1883, by Plowright of King's 

 Lynn, a physician quite isolated from direct scholastic influences. 



In the study of life-histories of rust-fungi, and in the introduction 

 of a culture method of observation now employed among all classes 

 of plants, as well as in many other ways, De Bary contributed greatly 

 to the advancement of mycology. The economic problem of the 

 cereal rusts, for which De Bary supplied an interpretation of the 

 most fundamental unknown quantity, transcends that of all others 

 in plant pathology, if measured by the annual money loss to the 

 cultivator in America, Australia, and possibly other countries. It 

 is yet an unsolved problem. De Bary's services culminated in his 



1 Davy, Elements of Agricultural Chemistry, 2d ed., p. 2G6, London, 1814. 



