2 FUNGOUS DISKASKS OK PLANTS 



Physiology and morphology. The progress in systematic my- 

 cology has made possible for more than half a century a compre- 

 hensive study of the diseases of plants ; yet systematic study alone 

 is not responsible for the rapid progress subsequently achieved in 

 plant pathology. A number of causes might be suggested as of 

 importance in the development of the latter field. It should not 

 be overlooked that advances in general plant physiology were also 

 manifest at about the beginning of the nineteenth century, and 

 that this phase of botany had undergone unusual development 

 toward the middle of the century, under the influence of Sachs 

 and other experimentalists of his time. Again, a more intensive 

 method in the study of morphology had been introduced, and in 

 mycology the efforts of such men as the Tulasne brothers had 

 shown what could be done in carefully following out the life his- 

 tories or development of the fungi. Beginning about the middle 

 of the nineteenth century, another distinctive epoch is entered 

 upon, and the developments of this period are due chiefly to Anton 

 de Bary and his contemporaries. 



The rise of plant pathology. De Bary became the conspicuous 

 leader in this field, establishing in an incontrovertible manner the 

 connection between the polymorphic stages of certain parasitic 

 species, and the possibility of following, under well-controlled con- 

 ditions, the development of little-known groups. His work was, 

 furthermore, particularly significant in that he so thoroughly appre- 

 ciated the nature of parasitism, the epidemic character of fungous 

 diseases of plants, and the practical value of methods of inoculation 

 and infection. To him more than to any one else we owe the influ- 

 ence which directed future work along the lines of the most profit- 

 able research. This period witnessed also the advances made by 

 Pasteur and others in the study of fermentation and disease, and 

 it was closely followed by those perfections in the development of 

 pure culture methods which have finally resulted in the possibility 

 of cultivating practically all bacteria and a very great majority of 

 the fungi. In the study of the fungi as the cause of plant diseases, 

 at this time, valuable service was also done by Kiihn, who in his 

 early career devoted himself particularly to a study of the fungous 

 parasites of cultivated plants. The last decades of the century yield 

 work of such diversity and importance that it is impossible he-re to 



