38 
BULLETIN 957, IT. S. DEPARTMENT OF AGRICULTURE. 
pine bearing aeeia. It was placed in a box in the laboratory and 
allowed to dry out. Tests were made by inoculating leaves of Ribes 
nigrum plants on May 7, May 21, June 4, and June 23. On the last 
date no infection occurred. In 1916, McCubbin repeated these 
experiments and found that the seciospores remained capable of 
infection under the conditions of his experiment at least 39 days. 
He believes they may retain viability considerably longer, as his 
tests were conducted under adverse conditions. 
iEciospores collected on April 9, 1917, and kept in a closed glass 
vial were tested by Gravatt weekly in hanging drops of distilled water. 
They gave good germination for about one month, then weakened 
until June 9, when the last germination occurred. The tests con- 
tinued until July 14. On May 7, 1917, another series of similar tests 
was started by Gravatt and Taylor. (See Table II.) The seciospores 
were placed in two glass vials with cheesecloth tied over the tops. 
One vial (B) was kept out of doors on a window sill on the north 
side of a building where the sun did not shine. The other vial (A) 
was kept in a dark refrigerator. The spores were tested weekly in 
distilled water. In most cases the cultures were placed in an ice 
box for about 12 hours. The spores kept in the ice box retained 
their color throughout, while those on the window sill had faded 
perceptibly by June 16. Lot A varied in germination from 8 per 
cent at first to 3 per cent on June 2. Germination persisted until 
July 2, when the last occurred in this lot. Lot B germinated freely 
until May 26 and not at all after June 23. Cooling and darkness in 
this case decidedly stimulated germination for one month and pro- 
longed viability about 10 days after the uncooled seciospores which 
were exposed to light had lost all viability. 
Table II.- — Longevity of the spores of Cronartium ribicola. 
' Germination (per cent). 
Date, 
1917. 
Lot A, vial in 
refrigerator. 
Lot B, vial out of 
doors. 
Notes. 
iEcio- 
spores. 
Uredi- 
nio- 
spores. 
Telio- 
spores. 
^Ecio- 
spores. 
Uredi- 
nio- 
spores. 
Telio- 
spores. 
May 8. 
May 12. 
May 19. 
May 26. 
June 2. 
June 9. 
June 16. 
June 23. 
Julv 2. 
July 7. 
July 14. 
8 
8 
5 
4 
3 
1 
.1 

.05 


13 
10 
60 
45 
6 
.65 
1.35 




90 
85 
80 
70 
40 
51.3 
4.5 
3.5 
.5 


8 
1 
2 
3 
.8 
.1 

.05 



8 
10 
40 
37 
.8 
1.5 


.1 


85 
90 
85 
50 
10 
4.4 


Notcooledinrefrigeratorbeforegermination. 
Do. 
Lot A somewhat faded. 
Lot A much faded. 
Teliospores in lot A mouldy. 
JEciospores and urediniospores mouldy in 
lot A, color of lot B still fairly good. 
