1915] 



BURT TIIELEPHORACEAE OF NORTH AMERICA. IV 637 



Exohasidium Andromedae Peck is based on the bag gall 

 produced by Andromeda ligustrina. This gall described in 

 detail on a preceding page, is so very large and remarkable in 

 structure that it did seem that here, if anywhere, must be the 

 anomaly for higher fungi of a fungous cause, specifically dif- 

 ferent from Exohasidium Vaccinii, yet having the same mor- 

 phological characters. From this point of view, Richards' 

 experiment,^ already described, of growing on the leaves of 

 Andromeda ligustrina a July crop of leaf concavity galls from 

 spores produced by a bag gall which had matured at the be- 

 ginning of July, was very illuminating. It showed that such 

 a bag gall is noteworthy only because it shows peculiar prop- 

 erties inherent early in the season in shoots and leaves of 

 Andromeda ligustrina, that this bag gall belongs in the series 

 with, and is caused by, the same fungus as the leaf concavity 

 galls such as Exohasidium Vaccinii produces. 



Richards made other experiments tending to show that E. 

 Vaccinii produces the bag galls on Andromeda ligustrina. 

 He demonstrated that the latter species is not immune to un- 

 doubted Exohasidium Vaccinii, that it is as susceptible to such 

 spores as to those produced by its own bag galls. In July, 

 spores of E. Vaccinii gathered from leaf concavity galls of 

 Gaylussacia resinosa were transferred to buds and young 

 leaves of Andromeda ligustrina. After about the same lapse 

 of time as when spores from the bag galls were used, there 

 appeared on the Andromeda leaves infected with Exohasidium 

 Vaccinii distortions very similar to those produced by spores 

 from the bag galls. As the large bag gall was the only occa- 

 sion for the name E. Andromedae Peck, I agree with Richards 

 that this name is a synomym of E. Vaccinii. 



In confirmation from the herbarium side of the correctness 

 of the above conclusion, I have a specimen collected in Idaho 

 by Professor Piper, 772, on Menziesia glahella, which has a 

 small terminal bag gall such as is produced by Andromeda 

 ligustrina, and also a leaf concavity gall. 



In the light of what we now know about bag galls the names 

 Exohasidium Azaleae, E. discoideum, and E. Rhododendri 



^ loc. cit. 



