SOME OBSERVATIONS ON THE DEVELOPMENT 
OF PERIDERMIUM CEREBRUM 
Ву B. О. Попсе AND J. Е. ADAMS 
Columbia University 
(WITH PLATES 4-6) 
The form of Peridermium Cerebrum Peck on Pinus rigida in 
the vicinity of Lakehurst, and Toms River, New Jersey, has 
presented several points of interest. Specimens of this fungus 
on P. virginiana from Bedford, Virginia, have been available for 
comparison through the kindness of Professor R. A. Harper. 
The prevailing type of infection observed in New Jersey 
appears as circular or elongated. canker-like swellings on trunks 
ranging up to eighteen inches in diameter. Where suckers de- 
veloped after trees had been cut down, the recent infections appear 
as globular or fusiform swellings. The canker-like swellings on 
the trunk are the common form of the fungus. Infections are 
frequently found at the base of the tree as well as at varying 
heights on the trunk, usually below the region bearing branches. 
The trunk infections often consist of a number of closely associated 
swellings, the outermost being smaller and younger developments. 
The galls vary in size and are circular or elliptical in outline. 
This difference in the shape of the swellings suggests that the 
infection may sometimes progress more rapidly in one direction 
than in the other. Stewart,* studying the globoid galls of P. 
Cerebrum on Pinus Banksiana, is of the opinion that the fungus 
spreads quite as slowly vertically as it does horizontally. In 
several cases at Lakehurst protuberant elongated swellings were 
found developing parallel with the trunk, and were at least six 
times as long as they were wide. On the other hand, the invasion 
of the host by the fungus is sometimes more rapid peripherally 
than it is vertically. The disease in this material obviously 
* Stewart, A. Notes on the anatomy of Peridermium galls. Am. Jour. Bot. 3: 
12—22. 1016. 
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