June is, 1914 
Peridermium 
249 
The chief difference between these two species of Peridermium, accord¬ 
ing to the original description of each, appears to be the formation of 
globoid swellings on the host tree attacked by Peridermium cerebrum 
(PI. XI, fig. 1) and of fusiform swellings by P, fusiforme (PI. XI, fig. 2). 
Both species have the cerebroid arrangement of the secia, while their 
seciospores and peridial cells agree closely in size, color, and shape. 
From a series of field observations made by the senior writer during 
the last four years it is established that in case of the swellings of Peri¬ 
dermium cerebrum on Pinus virginiana the pycnia precede the secia 12 
months, instead of preceding them during the same spring. In other words, 
the pycnia and secia occur during alternate years, and two years is the 
time required for a life cycle of all forms of spores of the rust. Usually 
only pycnia or only secia are found on a gall during the same season, but 
occasionally both are found on different parts of the same swelling. 
In such cases the part bearing pycnia does not bear aecia till the following 
spring and vice versa. In no case have both pycnia and secia been 
found at the same time, the one succeeding the other during the same 
season on the same portion of the surface of a swelling. 
The junior writer recently noted pycnia on the swellings caused by 
Peridermium fusiforme on pines in Florida. They were noted as occur¬ 
ring on separate swellings from those bearing secia, indicating the same 
alternation as in P. cerebrum. 
The field and cultural data here given prove conclusively that Peri¬ 
dermium fusiforme and P. cerebrum are both aecial stages of the same 
fungus, Cronartium cerebrum , and are not even sufficiently differentiated 
to constitute separate races. 
Arthur and Kern 1 also make Peridermium fusiforme a synonym of 
P. cerebrum . They state that this conclusion was reached from cultures 
made by them in 1913; however, their cultural data were not given in 
this article. 
1 Arthur, J. C., Kern, F. D. North American species of Peridermium on pine. In Mycologia, v. 6 , no. 
3 > P- 133-138. 
