226 PHYTOPATHOLOGY [VOL. 6 



The mycelium is unable to spread from the initial point of infection and 

 thus produce a gall at some distant point. 



The typical Peridermium harknessii very much resembles Peridermium 

 cerebrum Peck. Since Shear 4 has proved that Peridermium cerebrum 

 has as its alternate stage Cronartium Quercuum (Berk.), the occurrence 

 of a Cronartium on Quercus agrifolia in California 5 made it appear possible 

 that the two Peridermia were identical. Hedgcock and Long 6 call the 

 eastern form on oak Cronartium cerebrum. The identity of the Calif ornian 

 Cronartium on oak with the eastern form not being definitely proved 

 by inoculation, the old name Cronartium Quercuum in Shear's sense is, 

 for convenience's sake, used in this paper. 



The writer has found Cronartium Quercuum in its telial form in the im- 

 mediate vicinity of Pinus radiata only on Quercus agrifolia near Monterey, 

 Palo Alto and Menlo Park, California. Near the latter two places col- 

 lections were also made by Mr. J. T. McMurphy. Pinus radiata in its 

 natural range occurs only in an extremely limited area on the coast, but 

 is planted extensively. Quercus agrifolia is common along the coast 

 from Mendocino south, but does not even penetrate into the great valleys 

 of the Sacramento and San Joaquin Rivers, much less into the Sierra 

 Nevada, where Peridermium harknessii, so-called, is very common on 

 Pinus sabiniana, P. ponderosa and P.jeffreyi, and above all, on P. contorta. 

 In the regions inhabited by these pines other oaks, particularly Quercus 

 californica and Castanopsis chrysophylla are common, both of which Hedg- 

 cock has successfully inoculated with aeciospores of Peridermium cerebrum. 

 It is, therefore, still possible, that Quercus californica and Castanopsis 

 chrysophylla or perhaps some of the other associated oaks, may be the 

 alternate hosts of the so-called Peridermium harknessii on some of the 

 Sierra Nevada pines. Farlow and Seymour (p. 161) name Pinus ponder- 

 osa as a host for Peridermium cerebrum Pk. However, no Cronartium 

 has been found, to the writer's knowledge, on Quercus californica or Cas- 

 tanopsis chrysophylla in California. 



Cronartium Quercuum is by no means common on Quercus agrifolia 

 in the vicinity of Pinus radiata. In fact, one may say without exaggera- 

 tion, that there seems to be no direct relation between the distance of 

 oak from infected pines and the frequency of the Cronartium, even where 

 the oak is standing close to heavily infected pines. Never very abundant, 

 it is found as common on oaks standing isolated or one hundred to two 



4 Shear, C. L. Peridermium cerebrum Peck and Cronartium Quercuum (Berk.) 

 Journ. Myc. 12: 89. 1906. 



6 Arthur, J. C. North American Flora, 7 2 : 122. 



6 Hedgcock, G. G. and Long, W. H. Identity of Peridermium fusiforme with 

 Peridermium cerebrum. Journ. Agr. Res. 2: 247. 1914. 



