14 BULLETIN 247, U. S. DEPARTMENT OF AGRICULTURE. 



from an inch to more than a foot in length. In case of Pinus pungens 

 (PL II, figs. 1 and 2), fusiform swellings are not so common as in 

 case of Pinus contoria 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 aecia rup- 

 tures the bark of the diseased areas, forming numerous openings 

 (PL 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 93cia 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 waiter, 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 

 secia 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 secia 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. 



1 Boyce, J. S. Notes on Cronartium pyriforme. Unpublished report submitted December 7, 19H. 



