194 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
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 outbreak 
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 
gooseberry plants, the latest one being from Hexham, 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.26 Further, it is believed, but not 
conclusively proven, that aecidiospores can not infect pines and 
teleutospores can not infect currants. The uredospores 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 im- 
ported currants. However, some eminent mycologists have ex- 
pressed doubt on this point. Eriksson,?’ Fischer, Iwanoff,?® Nils- 
son,? and Speschneff,?! have all cited cases of the occurrence of 
Cronartium ribicola on currants in localities where Pinus strobus 
was lacking; and Eriksson,** particularly, has expressed 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, be- 
lieves that this view should not be accepted without thorough in- 
vestigation. In none of his numerous inoculation experiments was 
there a recurrence of Cronartium the following season. In our 
own case the outbreak on currants can not be satisfactorily ac- 
** See references given in footnote 7. 
* Eriksson (13 p. 382). 
= Hiscneny C15 ys 
™Iwanoff (22, p. 99). 
* Nilsson (45). 
** Speschneff (60). 
* Eriksson (13, p. 392). 
* Klebahn (33). 
