NUCLEAR BEHAVIOR IN PROMYCELIA 
43 
Caeoma nitens is a short-cycled rust which has no connection with 
Puccinia Peckiana, but it has seemed desirable to make further infec- 
tion experiments and to determine the nature of the mycelium that 
bears the teleutospores of Puccinia Peckiana. Clinton (5) figures the 
germination of these spores but he does not show the production of 
sporidia and from his drawings we cannot be sure that they are pro- 
ducing promycelia. I have, therefore, attempted to obtain further 
evidence along these lines. 
On May 15, three blackberry plants that were badly infected with 
Caeoma nitens were removed from Van Cortlandt Park and placed 
in pots in a greenhouse. Nine uninfected plants were also brought 
in and after they had started new growth and appeared to be in a 
healthy condition, five of them were, on May 28, heavily inoculated 
with fresh mature aecidiospores of Caeoma nitens. They were kept 
under bell jars for a few days in order to secure a moist atmosphere 
for the germinating spores. The other four uninfected plants were 
used as checks. The five plants that were thus inoculated, as well 
as the three plants that were badly infected at the time they were 
placed in the greenhouse, are at present in a vigorous condition and 
show no signs of being infected with Puccinia Peckiana. I have also 
had under observation several hundred plants in Van Cortlandt Park 
that were badly infected with Caeoma nitens during the early spring. 
All of these plants were free from Puccinia Peckiana at the end of the 
growing season and I have not been able to find this rust in the vicinity 
of New York City. 
To secure material of Puccinia Peckiana for study, a visit was made 
to a region near Old Forge, New York, in the Adirondack Mountains 
and to the vicinity of Glen, New Hampshire, in the White Mountains. 
In both of these regions, during the latter part of August, I found 
Puccinia Peckiana widely distributed and abundant on the leaves of 
Ruhus frondosus Bigel. Stained sections of infected leaves, made 
from material obtained on this trip, show that the vegetative cells of 
the mycelium are binucleate, figure 16. The cells of the teleutospores 
in young sori contain two nuclei, but in the older sori, the cells have 
become uninucleate, presumably b}^ the fusion of the two nuclei. 
Thus there is nothing unusual in the development of these teleuto- 
spores. 
Some of the teleutospores were also germinated. They were 
scraped from green blackberry leaves and were spread over the surface 
