SELECTED CYCLES IN GYMNOCONIA PECKIANA 8l 
perennial, for there was no evidence of the Caeoma in 191 7, on any 
of these experimental dewberry plants. 
One of the important problems still awaiting attack was the 
question as to whether or not the raspberry Caeoma with the one- 
generation cycle is biologically the same as the raspberry Caeoma 
with the two-generation cycle. Tropical and subtropical regions 
appear to be richer in rusts with the Endophyllum type of germination 
than do the temperate or subarctic regions. Caeoma nitens has long 
been known to have a much farther southern distribution than Puc- 
cinia peckiana and the recent interesting paper by Arthur clearly 
shows this. In consideration of these facts, an experiment was made, 
in June, 1 91 7, on the supposition that temperature might be, to a 
large extent, the controlling factor, determining the mode of germina- 
tion of the aecidiospores of the orange rust of the raspberry. This 
was taken as a working hypothesis, and the following experiment was 
carried out. 
Four of the experimental raspberry plants were sprayed with water. 
Aecidiospores from the dewberry plants of the same patch mentioned 
above were dusted on the leaves. This was done June 27, 191 7. 
Excelsior was packed close around the raspberry plants to support 
several blocks of ice. Each plant with its ice pack was then covered 
with a bell jar. These experiments were started at 5:30 P.M. The 
ice was not all melted in twenty-four hours. More ice was added on 
the afternoon of June 28, and additional aecidiospores were sown. 
The plants remained covered until the morning of June 30, when the 
bell jars and excelsior were removed. 
The plants were not closely examined again until August 2, 191 7. 
All four of the hosts showed infection. There were several leaves 
on each plant with yellowish spots and areas, bearing on the underside 
the minute projecting masses of teleutospores of Gymnoconia peckiana. 
On some of the smaller leaflets the sori were rather thickly scattered 
over the entire under surface. The teleutospores examined presented 
in a striking way the peculiar form characteristic of Puccinia tripustu- 
lata Pk. (24th Rept. N. Y. State Mus. Nat. Hist., 91, pi. 3, fig. 16, 
1872). ^ 
During the last week in August, 12 to 15 more leaves on the four 
experimental plants were found to be richly sprinkled with the te- 
leutosori. 
The check raspberry plants were close beside those in the chilled 
