WHITE-PINE BLISTER RUST. 33 
Observations by Pennington 17 on the aecia showed that more aecia 
were produced per canker and many new cankers were fruiting in 
1919, so that more sedospores were produced that year than in 
1918 in the Adirondacks. Observations on the first generation of 
uredinia and the results of spore- trap work indicated, however, that 
not as many aeciospores were set free in 1919 as in 1918. This is 
supposed to have been due to. heavy rains, which beat them down 
from the air. The distribution of the first generation of uredinia 
showed that the asciospores were as widely disseminated in 1919 as 
in 1918. 
DISTANCE OF DISSEMINATION OF THE ^CIOSPORES. 
As is true of many of the more difficult points in the life history of 
Cronartium ribicola, European statements concerning the distance 
that the asciospores are distributed are based apparently mostly on 
personal opinions. The value to be attached to these statements 
seems to rest on the known excellence, or the reverse, of the pub- 
lished work and judgment of the writer who is being considered. 
European mycologists have mentioned a number of instances where 
this fungus appeared on Ribes which were said to be far removed from 
white pines. But some of these cases were later found to be actually 
much nearer diseased white pines than was at first supposed. Tubeuf 
(166) has stated that the aeciospores spread the disease up to 500 
meters or more. On the other hand, a considerable number of 
definite recommendations for separation of the alternate hosts set a 
distance of only 30 to 100 meters (131, p. 41-42). 
In North America earlier field experience indicated that the 
asciospores spread the disease for rather short distances from their 
source. It was recognized from the beginning that these spores are 
exceedingly light and well adapted to wind dispersal, and it was stated 
that our knowledge of their dispersal was very limited. Special 
efforts have been made for three seasons to gather more data on this 
problem. 
Posey, in 1917, set bushes of Ribes nigrum in a salt marsh at Kittery 
Point, Me., at varying distances from infected pines before uredinia 
were formed. Some infection resulted from asciospores upon Ribes 
plants more than a quarter of a mile from any white-pine trees. 
The infecting spores probably traversed several hundred yards addi- 
tional, as the nearest pines were not known to be diseased. The 
heavily infected area was about 1J miles distant, and the infecting 
spores may easily have come that distance. 
Posey also examined the islands of the Isles of Shoals, off Ports- 
mouth, N. PL, for the presence of Cronartium ribicola . He found no 
pines, but a number of Ribes Jiirtellum plants. A few leaves were 
1- Pennington, L. II. Op. cil . 
46103°— 21— Bull. 057 3 
