3 1 8 Journal of Agricultural Research vd. xx, no. 4 



A square yard of vigorously growing alfalfa plants in the corner of a 2- 

 year-old plot was selected for inoculation. These plants were already 

 producing shoots 1 foot or more in height. The soil and debris were 

 carefully scraped away from around the crowns of these plants, exposing 

 a large number of developing buds and shoots. The inoculum was care- 

 fully packed around these crowns, the growing tops of which were finally 

 sprinkled and dusted with crushed galls. Sphagnum was packed over 

 and around the plants to a depth of 2 or 3 inches, water was sprayed 

 over the plot, and the sphagnum and soil beneath were kept thoroughly 

 wet for 10 days. On June 1 the material was removed from around the 

 plants, but no trace of any infection was discovered. Whether the rapid 

 growth which the plants were already making at the time when inocu- 

 lation was made prevented infection or whether some other circumstance 

 was responsible for the failure can not be told until further work is done. 

 From observations which were made in the field, it appears probable 

 that most of the warts which developed that spring resulted from infec- 

 tions which had taken place previous to the date at which the inocula- 

 tion was made. Thus it is possible that at the late date at which the 

 experiment was begun the spores of the fungus had in large part ceased 

 to germinate, or the plant itself might have passed its period of greatest 

 susceptibility. 



Inoculations of plants in the greenhouse at Washington gave two 

 instances of successful infection. In one case a pot of seedling plants 

 about 6 inches tall were inoculated by replacing the dirt around the 

 crowns with crushed diseased tissue and debris from plants recently 

 received from California. Inoculation was made October 1, and on 

 January 3 three plants with very young infections were found. 



Attempts to obtain infected plants by sowing seed in soil to which 

 crushed warts had been added usually resulted in the destruction of the 

 young plants by Rhizoctonia and possibly other fungi introduced with 

 the inoculum. In one case, however, among nine plants from seed 

 mixed with Urophlyctis spores and sown in April there were found in 

 the following January three infected plants, two of which were dwarfed 

 and much injured by the disease. If it were possible to obtain a large 

 percentage of plants in the field as badly infected as those in this experi- 

 ment, this disease would be capable of much harm. As a matter of 

 fact, however, only a relatively small percentage of young plants have 

 been found infected in the field even under what would appear to be the 

 most favorable conditions. 



When germination of spores can be obtained with some degree of cer- 

 tainty or when field experiments under suitably controlled conditions 

 can be freely undertaken, opportunity will be open for further infection 

 studies that should add to our meager knowledge of the conditions 

 necessary for infection in the field. 



