14 BULLETIN 247, TJ. S. DEPARTMENT OF AGRICULTURE. 
from an inch to more than a foot in length. In case of Pinus pungens 
(PI. II, figs. 1 and 2), fusiform swellings are not so common as in 
case of Pinus contorta and Pinus ponderosa. Swelling is commonly 
not very evident in very young trees of any of these three species. 
The bark layers are usually thickened in the portions where the rust 
mycelium is present. So far as can be ascertained from field observa- 
tions the secia may not appear until three or more years after infection 
takes place. 
The development of the peridia at the maturity of the ascia rup- 
tures the bark of the diseased areas, forming numerous openings 
(PI. II, fig. 2) which reach to the inner layers of the cambium. As a 
result the death of the cambium layer may take place, due apparently 
to excessive evaporation of water through the lesions. The part of 
the tree attacked usually is either girdled and killed outright or it is 
partially girdled and a canker is formed. Young pines are very 
commonly girdled and killed during the same season the aacia are 
produced. In its effect on pines, Peridermium pyriforme must be 
classed with P. strobi and P. filamentosum and be ranked as one 
of the most destructive species of Peridermium in North America. 
In a region adjacent to Greenwood Furnace, Huntingdon County, 
Pa., the senior writer, during June, 1914, took notes on the number 
and condition of pines (Pinus pungens) diseased with Peridermium 
pyriforme. Again, in autumn, the condition of the same trees was 
noted, and it was found that of 50 diseased pines upon which the 
ascia had been found in June, 29 (58 per cent) were dead from the 
girdling effect of the fungus. 
These had apparently died shortly after the ascia fruited, as dead 
leaves were still clinging to the branches of the trees. The pines ex- 
amined were small, varying in height from 4 to 10 feet, and in diam- 
eter at the ground from 1 to 4 inches. A similar effect was noted 
during the autumn of 1914 on a smaller number of young pines 
(Pinus ponderosa) in the Black Hills near Custer, S. Dak. 
J. S. Boyce, of the Office of Investigations in Forest Pathology, has 
reported this fungus on the yellow pine (Pinus ponderosa) in Klamath, 
Shasta, and Trinity National Forests in California. 1 This report 
states that in the Klamath National Forest — 
The parasite produced spindle-shaped swellings at the point of infection on the 
yellow pine, usually on the main stem but occasionally on the branches. These 
swellings varied from 2 inches to a foot in length. 
The fungus on yellow pine undoubtedly kills that portion of the main stem or branch 
of the tree above the point of infection. A number of small trees were found to have 
been killed. Each of these bore one or more spindle-shaped swellings on the stem. 
A volunteer (shoot) had then appeared while a new infection had occurred just 
below the point where the volunteer joined the main stem. A repeated killing of 
this kind causes a strikingly deformed tree. 
i Boyce, J. S. Notes on Cronartium pyriforme. Unpublished report submitted December 7, 1914. 
