INTERSPECIFIC TRANSMISSION OF MOSAIC DISEASES 



OF PLANTS 1 



Karl Hermann Fernow 



The subject of mosaic diseases is one of great and increasing importance 

 in plant pathology. A large number of economic plants and many wild 

 species are known to be affected. The question of the intercommunica- 

 bility of mosaic diseases among different suscepts is still largely an 

 unanswered one. Many reports in literature on attempts to transmit 

 them are merely incidental to other investigations, and leave the reader 

 in doubt as to the methods employed and as to the extent of the experi- 

 mental work on which conclusions are based. In many cases reports 

 of different investigators are in conflict. 



The purpose of the studies here reported is to determine: (1) whether 

 the mosaics of different plants are due to distinct causes, here called 

 viri, or whether all are due to a single virus; (2) if the causes are several, 

 what plants are affected by each; and (3) what are the symptoms produced 

 by the different viri on various suscepts. Obviously it is impossible to 

 fully answer the above questions in an inquiry as brief as this. 



The experiments described were carried on in the greenhouses of the 

 Department of Plant Pathology at Cornell University, and on the experi- 

 mental farm, during the years 1922, 1923, and 1924. 



ACCOUNT OF EXPERIMENTAL WORK 

 MATERIALS 



Source of inoculum 



For the sake of convenience, the various sources of inoculum are desig- 

 nated by the letters A to H. As is shown later, these different sources 

 represent also different viri, at least in part. The original sources of 

 the inoculum designated by these letters were respectively as follows: 



A. Juice of mosaic tobacco plants kept in a bottle in the greenhouse for 

 several years but still found to be infective. 



B. Mosaic potato plants grown from tubers collected in the field in 

 various parts of New York. Also, plants grown from tubers sent to the 

 writer by Dr. Donald Folsom, of Maine, which represent the various 

 types of mosaic described by Schultz and Folsom (1923). Although these 



1 Also presente 1 to the Faculty of the Graduate Scho '1 <>f C irnell University, June, 1925, as a major 

 thesis in partial fulfillment of the requirements for the degree of doctor of philosophy. 



