232 PHYTOPATHOLOGY [VOL. 6 



the immediate vicinity of heavily infected Pinus radiata and its apparent 

 absence on oaks and Castanopsis of the Sierra Nevada suggests the pos- 

 sibility that infection of what we call Peridermium harknessii on Cali- 

 fornia pines may take place directly from pine to pine by means of aecio- 

 spores. This, of course, does not exclude the possibility of infection by 

 sporidia, where Cronartium on oaks is present. 



The idea in itself is not a new one. Eriksson, 15 in discussing the prob- 

 able mode of dissemination of Peridermium Pini, for which no alternate 

 host was known, came to the conclusion, without adducing any proof 

 however, that infection must take place directly from tree to tree. Kle- 

 bahn (pp. 40 and 380) on the other side considers the formation of aecia 

 of heteroecious fungi from aeciospores or spermatia as a priori improbable. 

 Mentioning Eriksson's failure to report a successful outcome of his direct 

 inoculation experiments he even goes so far as to say "Es kann also hiernach 

 auch als ziemlich sicher angenommen werden, dass eine Infektion der 

 Kiefer mittels der Aecidiosporen nicht moglich ist." Hedgcock, accord- 

 ing to recent personal information, has tried direct inoculation with nega- 

 tive results. 



EXPERIMENTATION 



In the following, the results of the writer's experiments are given. 

 The aecial material used was collected on the morning of May 22, 1913 

 from richly sporulating galls of typical Peridermium harknessii on Pinus 

 radiata at Sausalito, Marin County, California, where the fungus is very 

 common, but where in spite of the most careful and continued search 

 no Cronartium could be found on the native Quercus agrifolia. Other 

 oaks or Castanopsis do not occur in the vicinity. The material was 

 kept dry and taken at once to San Francisco, California (a distance of 

 a few miles only). The plants used for the inoculation experiments 

 consisted of a series of four young trees of Pinus radiata (3-years-old) in 

 pots, from a reliable nursery. They were about two to two and one-half 

 feet high, in perfect health, thrifty and without a sign of Peridermium. 

 We will designate them as I, II, III and IV. They were kept in the labora- 

 tory, in the center of San Francisco, where contamination from the out- 

 side is out of the question and where there existed no possibility of in- 

 fection through sporidia from Cronartium on oak. 



On May 22 and May 23, 1913, No. I was inoculated in seven places of 

 different ages with aeciospores suspended in water, by wounding the 

 sprayed bark with a sterilized needle and gently rubbing the infection 



]5 Eriksson, J. Einige Beobachtungen iiber den stammbewohnenden Kiefern- 

 blasenrost, seine Natur und Erscheinungsweise. Centralbl. Bact. II Abt. 2: 385. 

 1896. 



