1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 229 



The infection of the oak leaves is not heavier in the lee of pines with 

 richly sporulating galls than in other sites, although here, close to the 

 ocean, the prevailing winds are very constant. The very uneven dis- 

 tribution of the fungus on Quercus agrifolia may find its explanation 

 in racial characteristics and susceptibilities of the oak. The telial form 

 on Quercus agrifolia is even less frequent than the uredenial form. The 

 writer has found the latter locally plentiful on Quercus densiflora and 

 Quercus chrysolepis along the Coast to the Oregon line, always with- 

 out the telial form. On the * Klamath River in the northwestern part 

 of California near the coast the writer collected a uredenial form on 

 Quercus chrysolepis, which caused a distinct witches'-broom. Possi- 

 bly this is a new form; the formation of witches'-brooms, it seems, has 

 never been observed in other uredinial infections on oak. Another 

 Cronartium received through the courtesy of Messrs. J. T. McMurphy 

 and J. W. Sheldon was collected in the middle of May in the Coast Range 

 near Palo Alto, California on Quercus durata. Quercus durata is an ever- 

 green shrub. The collection comes from a region where Peridermium 

 harknessii is common on Pinus attenuata and P. radiata. Whether any 

 of these pines occurred in the immediate vicinity of the infected oaks 

 is not known. 



Hedgcock 7 was successful in infecting several California oaks (Quercus 

 lobata, Q. densiflora, Q. calif ornica) and also Castanopsis chrysophylla 

 with aeciospores from Peridermium cerebrum. His inoculations of two 

 pines, Pinus ponder osa and P. murrayana (contorta), which are common 

 bearers of the so-called Peridermium harknessii in California, with telio- 

 spores, supposedly from Quercus rubra, produced typical galls of Peri- 

 dermium cerebrum. On the other hand, his inoculations of oaks with 

 material of Peridermium harknessii on Pinus radiata from California, 

 failed. 



In 1912 Hedgcock 8 again reports that "repeated and careful inocula- 

 tion with aeciospores of this Peridermium (P. harknessii) on the leaves 

 of young oaks of a number of species failed to infect them, while at the 

 same time, inoculation with Peridermium cerebrum Peck on the same species 

 of oak trees brought about an infection, resulting in the uredinia and telia 

 of Cronartium Quercuum (Brond.) Arth." 



The possibility that these failures were due to loss of viability of the 

 spores in transit prompted the writer repeatedly to try inoculations with 

 fresh material on Quercus agrifolia and Q. californica. All these attempts 

 were without success. 



7 Notes on Peridermium cerebrum Peck and Peridermium harknessii Moore. 

 Phytopath. 1:131. 1911. 



8 Mycologia 4: 143. 



