34 BULLETIN 957, U. S. DEPARTMENT OF AGRICULTURE. 
found infected with the fungus. In 1920, Snell reexamined these 
islands much more carefully. He again found the fungus on several 
leaves and decided that it is evidently a case where the seciospores 
were blown from infected pines to the islands. The islands are about 
7 miles from the mainland, so that it appears that the aeciospores may 
be blown this distance and infect Ribes. There appeared to be no 
reason for thinking the fungus wintered over. At any rate, it must 
have come from the mainland originally. The islands where the 
disease was found are very seldom visited, so carriage of spores in 
this way appears to be eliminated. 
McCubbin (88) found that the asciospores fall about 8 feet in seven 
minutes in still air. This indicates a very wide potential distribution 
of these spores by a moderate breeze. 
In 1918, York and Overholts (cited in Spaulding. 145) worked in 
the White Mountains of New Hampshire in a generally infected 
region. Much work was done with spore traps and much time spent 
in examination of Ribes plants which were isolated from white pines. 
The work proved that the seciospores are distributed for miles to the 
tops of adjacent mountains approximately 3,000 feet high, that they 
arrive in a viable condition, and that they are the means by which 
the disease spreads far and wide to Ribes. 
In 1918, also, Pennington and Snell (cited in Spaulding, 145) 
worked in the eastern Adirondack region of New York. Spore traps 
here gave valuable contributory evidence, but study of the distribu- 
tion of the first generation of urediniospores with reference to neigh- 
boring white pines gave the best results. Here it was found that 
spore traps caught aeciospores up to 550 feet from any pines. Within 
a large area of cultivated land at Essex, N. Y., an intensive study was 
made by Snell (128) of the first generation of urediniospores. In this 
area the Ribes were found to have first-generation uredinia sparingly 
and widely scattered; that is, the seciospores causing the infection 
evidently came from a considerable distance. In one case diseased 
Ribes were found three-fourths of a mile from any white pine. 
Several others were found at smaller distances from any pine trees. 
It was concluded that the asciospores came from a distance of not less 
than three-fourths of a mile and probably much farther. 
These conclusions concerning the wide spread of aeciospores in the 
two localities were arrived at independently and without the knowl- 
edge by either party of what conclusions had beenreached by the other. 
In 1919, Snell (128) found near Rush Lake, Minn., infections on 
Ribes leaves which were 134 nriles from the nearest pine and about 
3 miles from the nearest known diseased pine. Many such infections 
were found in the same general area which were half a mile or more 
from any pine. These infections were found developing when the 
first generation of uredinia appeared throughout that general in- 
