1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 237 



radiata, P. ponderosa, P. attenuate,, and P. sabiniana furnishes new evi- 

 dence for the assumption that the two forms on the hosts named are 

 identical, without, of course, proving it. 



FACULTATIVE HETEROECISM OF PERIDERMIUM HARKNESSII 



The experiments prove that Peridermium harknessii is able to infect 

 at least Pinus radiata directly by aeciospores, that is, with omission of 

 the telial stage, if there is any. In other words, although it is highly 

 probable that the fungus is heteroecious, this heteroecism must be facul- 

 tative. The same is very probably true for the so-called Peridermium 

 harknessii on Pinus attenuata and P. contorta and perhaps for that on the 

 rest of the Sierra Nevada species of pines. 



Haack 20 published one year after the writer began his experiments, 

 and, of course, independently positively results of direct aecial inocula- 

 tion of Peridermium Pini on Pinus sylvestris. His first experiments 

 were inconclusive; he, therefore, later inoculated pines already heavily 

 infected, reasoning that these individuals would be more susceptible to the 

 disease. This latter procedure together with the fact that he operated 

 entirely in the open, already infected forest, makes his otherwise valuable 

 experiments inconclusive. The results of my inoculations of Pinus radiata 

 with Peridermium harknessii lend a strong support to the outcome of 

 Haack's experiments. 



Like others before him, Haack suspected that wounding of the bark 

 is a prerequisite for successful inoculation and assumes that insects are 

 largely responsible for such injuries. Hedgcock 21 states that "in nature, 

 young Peridermium galls are often found associated with wounds made 

 by an insect." On older parts of the tree the fungus "may gain entrance 

 through wounds made by birds (sapsuckers), but this hypothesis remains 

 to be proven." 



All the writer's observations go to show that insects play an impor- 

 tant, if not a decisive, role at least in direct aecial infection of the fungus 

 from pine to pine. The common presence of old wounds in connection 

 with Peridermium harknessii galls and the type of distribution of the 

 galls on the individual tree as well as on a group of trees speak against 

 promiscuous infection from a shower of wind-borne spores. When the 

 infection is not general, the galls are usually found only up to a certain 

 relative height, depending on the height and crown development of the 



20 Haack. Der Kienzopf (Peridermium pini (Willd.) Kleb.) Seine tTbertragung 

 von Kiefer zu Kiefer ohne Zwischenwirt. Zeitschr. Forst- und Jagdw. 46: 3-46. 

 1914. 



21 Phytopath. 1: 132. 



