234 Report of the Department of Botany of the 



that black currants in the immediate vicinity of this grove were 

 free from rust is proof that the source of the infection was not to 

 be found there. 



These recurring outbreaks of felt-rust on currants, seemingly 

 without any relation to the aecial stage on the pine, made it appear 

 highly probable that the fungus over-winters on currants as Eriks- 

 son has suggested. This is a matter of considerable importance. 

 If the fungus over-winters on currants the disease may be spread 

 through the distribution of affected plants by nurserymen. Accord- 

 ingly, the writers undertook to solve the problem. 



Spaulding 3 having suggested that the fungus may, perhaps, over- 

 winter by the formation of uredinia on the young shoots we first 

 made a careful examination of the buds and bark of a large number 

 of diseased currant plants. Although every leaf on these plants 

 was yellow with rust no sign of uredinia or telia was found either 

 on the buds or the bark. 



GREENHOUSE EXPERIMENTS. 



The next attack on the problem was by means of a series of experi- 

 ments in which affected plants, after being given a short period 

 of rest, were placed in greenhouses, forced into growth, and the new 

 leaves watched for the appearance of Cronartium. The plants 

 used in these experiments were yearling black currant (Ribes nigrum) 

 plants from a nursery near the Experiment Station. They had 

 been under close observation for some time prior to the falling of 

 the leaves and it is known that every plant had been abundantly 

 infested with Cronartium. They were dug November 19, 1912. The 

 few leaves still clinging to them were removed. Twelve of the plants 

 were sent to Dr. J. C. Arthur, Lafayette, Ind.; 24 to Dr. G. E. Stone, 

 Amherst, Mass.; 50 to Dr. G. P. Clinton, New Haven, Ct.; 200 to 

 Dr. Perley Spaulding, Washington, D. C; 100 to the junior author 

 at Ithaca, N. Y.; and the remaining 100 were retained by the senior 

 author for use at Geneva, N. Y. 



Under date of May 23, 1913, Dr. Arthur reports as follows con- 

 cerning the plants sent him: " The plants were left out-of-doors and 

 subject to the changes of weather until February. They were then 



3 Spaulding, Perley. The blister rust of white pine. U. S. D. A. Bur. PI. Indus. 

 Bui. 206:31. 1911. 



