ing the origin of Crorwrtium rlbicola is that its original host was 

 the Swiss stone pine, Pinus cembra, and that it was introduced 

 into Germany in recent times from Russia where Pinus cembra 

 forms extensive forests. Schellenberg expressed the opinion that 

 it is also indigenous in the Swiss Alps on Pinus cembra. 



It is altogether probable that the apparent absence of Cronar- 

 tium ribicola from America is real; or at least the fungus cannot 

 have existed here long. It is unlikely that collectors have over- 

 looked it. Both on the currant and on the pine it is conspicuous 

 and readily identified. The horn-like masses of teleutospores are 

 characteristic and serve to distinguish it from other rusts occur- 

 ring on Ribes leaves. 



ORIGIN OF THE GENEVA OUTBREAK. 



It would be interesting to know the origin of the outbreak 

 at Geneva, but from the data now in hand it is not possible 

 to locate definitely the original source of infection. It is likely 

 that the fungus was imported with pines rather than with cur- 

 rants or gooseberries, since it is perennial within the steins and 

 branches of the pine, while on Ribes it is confined entirely to the 

 leaves. The only white pines in the immediate vicinity of the 

 diseased currant plantation are two small trees standing 125 

 feet to the west. These were purchased from a Geneva nursery 

 and set eight years ago. From a careful examination of these 

 trees made in November they appeared in thrifty condition with- 

 out any indication of Peridermium. Nevertheless, they may be 

 the source of infection, notwithstanding their seeming freedom 

 from disease. Peridermium strobi should be sought in April and 

 May ; by November it is difficult to recognize. 



The two trees just mentioned are the only white pines on the 

 Station grounds ; and there are no specimens of Pinus cembra, P, 

 lambertiana, P. monticola or any other Pinus having leaves in 

 clusters of five. The nearest other possible sources of infection 

 are a 12-feet-high Pinus strobus sixty rods east, an aged Pinus 

 strobus about eighty rods north and a sixteen-year-old Pinus cem- 

 bra the same distance to the southeast. There are several nur- 

 series in the vicinity of Geneva and it may be that some one of 

 them has imported diseased pine trees. The nearest nursery con- 

 taining pines liable to the disease is about one-half mile west 

 of the Experiment Station. It contains a block of Pinus cembra 



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