and some Pinus strobus imported from France. Here may be the 

 source of infection. However, contradictory evidence is found 

 in the fact that a plantation of red currants (Ribes rubruin) di- 

 rectly across the road from this nursery was practically free from 

 Cronartium. A careful search revealed just one leaf affected with 

 Cronartiwn ribicola, which was in the teleuto stage. Another 

 plantation of red currants between the nursery and the Experi- 

 ment Station was entirely free from Cronartium. In fact the 

 single affected leaf above mentioned is the only instance in which 

 the Cronartium has been found outside the Station grounds al- 

 though the neighboring currant plantations were carefully 

 searched. Thus, the indications are that the source of infection 

 is on the Station grounds. 



This raises the question whether it is possible that the out- 

 break may have resulted from uredo- or teleutospores brought 

 onto the Station grounds with imported currant plants. During 

 the past ten years the Station has made several importations of 

 currant and goseberry plants, the latest one being from Hex- 

 ham, England,, in the spring of 1904. Can these plants have been 

 the source of infection ? It has already been stated that the 

 aecidium stage of Cronartium ribicola occurs on certain species 

 of Pinus, especially P. strobus. It has been proven that the uredo 

 stage on the currant may start from infection with aecidiospores 

 from the pine ; and that the aecidium stage on the pine may result, 

 from infection with teleutospores from the currant. Further, it 

 is believed, but not conclusively proven, that aecidiospores can not 

 infect pines and teleutospores can not infect currants. The uredo- 

 spores may infect currants directly, but they do not survive the 

 winter. In short, in the absence of pines the currant rust can not 

 perpetuate itself. This is the generally accepted view and if it is 

 a correct one the Geneva outbreak of currant rust could not have 

 come directly from imported currants. However, some eminent 

 mycologists have expressed doubt on this point. Eriksson, Fischer, 

 Iwanoff, Nilsson, and Speschneff have all cited cases of the occur- 

 rences of Cronartium ribicola on currants in localities where 

 Pinus Strobus was lacking; and Eriksson, particularly, has ex- 

 pressed the opinion that it may live from year to year on currants 

 entirely independent of the aecidium stage on the pine. Klebahn, 

 on -the contrary, believes that this view should not be accepted 

 without thorough investigation. In none of his numerous inocula- 



13 



