Hedgcock: Notes on Western Uredineae J 43 



Peridermium filamentosum apparently has been held in limited 

 areas for a long time by natural boundaries to certain forests, viz., 

 the treeless region separating the mountain ranges in Colorado, 

 New Mexico, and Arizona. The fungus should be made the sub- 

 ject of further investigation, and watched closely, since its effect 

 on seedling trees is much like the dreaded Cronartium ribicola 

 Fischer {Peridermium strobi Kleb.) in Europe. It certainly 

 should not be allowed to invade any of the forest tree nurseries in 

 the West, from which it might be disseminated over a much greater 

 region than its present habitat, and as a result great damage be 

 done to our magnificent western yellow pine and related species. 



2. Peridermium harknesii Moore 



This species of Peridermium is found attacking the following 

 species of pines in our western forests : Pinus contorta Loud., P. 

 Jeffreyi " Oreg. Com.," P. ponderosa Laws., P. radiata Don., and 

 P. sabiniana Dougl. The range of the species is from Colorado 

 northward to Montana, and westward to Washington, Oregon, 

 and Cahfornia. It is most common on the lodgepole pines in 

 the forests of the Rocky Mountains. 



Peridermium harknesii has an effect on pines almost identical 

 with that of Peridermium cerebrum Peck on pines in eastern and 

 central United States. Globose or oblong galls or burls, varying 

 in diameter from a pea to more than a foot are formed, usually 

 surrounding the twigs, limbs, and trunks at the point of attack. 

 Rarely a witches broom formation of limbs or twigs just above 

 the galls takes place. Young trees attacked are often killed by 

 the interference of the galls with the growth beyond the point of 

 attack. In such cases the galls apparently have a strangulating 

 effect. The fungus persists in the cambium of the galls for many 

 years, but as in case of Peridermium cerebrum, rarely fruits 

 annually. Apparently the older the galls become, the less fre- 

 quently the aecia are formed on the surface. 



Repeated and careful inoculation with aeciospores of this Peri- 

 dermium on the leaves of young oaks of a number of species 

 failed to infect them, while at the same time, inoculations with 

 Peridermium cerebrum Peck on the same species of oak trees 



