902 
Journal of Agricultural Research 
Vol. XXXI, No. 10 
THE MATERIAL 
CHARACTER OF THE MATERIAL 
Twenty-one collections of leaves bearing abundant telial columns 
were obtained from eight species of Ribes (see Table IV for their 
names) 3 in various parts of New Hampshire and northern New York. 
This material was about as unfavorable tor our purpose as could ordi¬ 
narily be obtained, because in some places there were prolonged 
local droughts which resulted in sparse telial production and pre¬ 
vented obtaining freshly matured columns (17, p. 63). Penning¬ 
ton (13) in 1920, because of the evenly scattered distribution of the 
rains during that summer, could get but few viable sporidia of 
Cronartium ribicola, in an area which generally is heavily infected, 
before the first week of September. In other places it rained fre¬ 
quently enough to partially germinate the telial columns as soon as 
they were formed. 
The amount of pregermination (i. e., germination previous to the 
collection of the infected leaves) of the telial cqlumns varied greatly. 
The average pregermination of the different collections of leaves 
ranged from 0 to 60 per cent. In most cases it was below 15 per 
cent. On the different leaves of a given collection the pregermina¬ 
tion often varied from 0 to 100 per cent of all of the telial columns 
examined. There was also a similar variation in the average pre¬ 
germination of the telial columns on the different parts of a single 
leaf. A telial column which showed one or more germinated telio- 
spores was counted as pregerminated. In such a column there might 
be left a thousand (19) or more teliospores which were perfectly 
viable when placed under favorable conditions for germination in 
the subsequent tests. 
In damp-chamber tests made immediately after collection of the 
material, the average germinability of the tenal columns (based upon 
the column as a unit) varied in the different collections from 7 to 
97 per cent. In more than half of the collections it was over 70 
per cent. The viability of the teliospores on different leaves and on 
different parts of the same leaf varied just as did the pregermina¬ 
tion for the same units. 
While these conditions hindered the writers in getting entirely con¬ 
sistent results, and certainly prevented the obtaining of maximum 
longevity, they also forestall any criticism for having worked with 
unduly favorable material. 
CONDITIONS DURING STORAGE OF THE MATERIAL 
The infected Ribes leaves were taken to the field laboratory as 
soon as feasible after collection. There they were laid singly upon 
newspapers and allowed to dry in the open air, where they were 
E rotected from direct sunshine. As soon as the leaves were wilted, 
ut not crisp, they were placed in mosquito-netting bags and hung 
out of doors fully exposed to the rain and wind but not to very much 
sunshine. After rains, when the leaves had begun to dry, they were 
shaken up so that they would not become matted into a solid mass. 
An attempt was made to simulate the conditions affecting naturally 
fallen leaves which had caught among shrubbery in the forest. 
* The nomenclature followed is that given in Coville and Britton ( 6 ). 
