1915] 



BURT THELEPHORACEAE OF NORTH AMERICA. IV 635 



occurrence in North America in a series of E. Vaccinii forms 

 confirms the correctness of the reference. 



As we take up the consideration of North American species 

 of Exohasidium which have been published since 1867, we find 

 that in nearly all cases peculiarities of galls have furnished 

 the distinctive portion of the description. These odd or strik- 

 ing forms of galls have been discovered upon new hosts, as 

 was to be expected, for a new host species would without doubt 

 have composition and properties at least slightly different 

 from those of Vaccinium vitis-idaea — so different that the 

 growth response, i. e., the gall of this new host, might differ 

 somewhat, perhaps differ notably, from that of V. vitis-idaea, 

 even though the stimulus should be given by the same fungus. 

 Two of the specific names to be considered are based entirely 

 upon the occurrence of Exohasidium on a new host, and the 

 other eight are founded upon more or less noteworthy galls. 

 Reference to the second division of my table shows that gall 

 form rather than host has caused the publication of specific 

 names in Exohasidium. 



Exohasidium Peckii, for example, was published as the 

 cause of flower galls produced by Andromeda Mariana. Its 

 flower galls are produced so frequently that they attracted 

 attention; leaf concavity galls are common here also. The 

 morphological characters of the fungous cause of these galls 

 agree closely with those of Exohasidium Vaccinii, and the 

 galls themselves are of types that Vaccinium vitis-idaea pro- 

 duces under stimulation by Exohasidium Vaccinii. No evi- 

 dence of any nature has been offered tending to show that E. 

 Peckii is not E. Vaccinii in all respects. The frequent pro- 

 duction of flower galls by Andromeda Mariana can be simply 

 accounted for as due to the susceptibility of the young flower 

 to infection by the fungus, that is, to a special property of 

 this host. I regard Exohasidium Peckii as a synonym of E. 

 Vaccinii. 



In connection with the discussion of E. Peckii, attention 

 should be called to occasional flower galls produced by Lyonia 

 {Andromeda) ferruginea. I have seen only four specimens 

 of these galls, two from Georgia and two from Florida. All 



