Nov. 15, 1925 
Longevity of Teliospores of Gronartium ribicola 
903 
At Warrensburg, N. Y., rain fell in quantities sufficient to wet the 
foliage on 26 different days, while at Bethel, Vt., this occurred on 
but 2 days. At the former place there were 7 periods of more than 
36 hours when the relative humidity of the air remained above 70 
per cent. This condition is shown by the work of the writers to be 
favorable for the sporidia to retain viability for a long time, and is 
discussed in their paper on the sporidia of Gronartium ribicola . 4 
SAMPLING THE MATERIAL 
In order to have representative material for each test, about half 
of the leaves used in each sample were taken from the middle of the 
storage bag and the remainder from the outside. The samples were 
taken after the dew had evaporated. Each sample was placed in a 
clean, dry Petri dish. 
PRECOOLING THE MATERIAL BEFORE TESTING IT 
Because it has been generally supposed that precooling per se 
stimulates the germination of the spores of the Uredineae (7, 5, 9, 
10, 16, 17, 21), it was thought best to-precool the material before 
starting germination of the teliospores. In the first two tests this 
was done by placing the Petri dishes containing the leaf samples in 
an ordinary refrigerator for about 24 hours. The material for the 
other tests, with the exceptions noted in Table IY, was placed in 
the Petri dishes and these then put in a metal container, which 
was packed in cracked ice and coarse salt for about 24 hours. The 
temperature thus obtained was certainly lower than that in the 
refrigerator, although no records were kept. The nightly hard 
frosts, which began about October 10, were considered to have the 
desired cooling effect, and the material was not further precooled 
in the tests run after that date. There was a marked increase in 
germination of some of the material beginning October 17, the date of 
the first test run after the frosts began. A suggested explanation 
is given below. 
Table I gives a comparison of germination of precooled and of 
nonprecooled telial columns. The results are fragmentary because 
the work was done late in the season, when suitable material was 
scarce; earlier it was supposed that the effect of precooling was 
thoroughly established by other workers, and the need for further 
testing this point was not realized. In the tests recorded in Table I, 
half of the tested material was precooled by packing the Petri dishes 
containing it in a mixture of salt and ice for about 24 hours; the 
other half of the material was kept at room temperature for the same 
length of time. The two methods of comparing the germination of 
the two samples of material show that the germination was prac¬ 
tically equal in the first two lots of Table I which are' designated 
there as “Fresh telial columns” and “Old telial columns stored 
indoors.” In the lot designated as “Old telial columns stored out¬ 
doors,” the same methods of comparison show that the uncooled 
telial columns germinated better; that is, those stored at relatively 
low temperatures and then subjected to higher temperatures reacted 
* Spaulding, P., and Gravatt, A. Rathbun. the influence of physical factors upon the via¬ 
bility of the sporidia of cronartium ribicola fischeb, 1925. fUnpublished manuscript.] 
