it has frequently been observed in the medullary tissues of the apothe- 

 cial stalks of Gyrophora and in the hypothecium of other lichens. 

 The reaction is, however, by no means constant and can not be con- 

 sidered as of value in the determination of species. 



With regard to the algae it may be stated that they react like nor- 

 mal free species ; they seem to have undergone no marked chemical 

 changes since their association with fungi to form lichens. 



