162 Mycologia 



a decoction from carrots solidified with gelose. Mycelium ob- 

 tained from spores of Morchella was vigorous, but no fruit-bodies 

 were formed, probably owing to the necessity of a mycorhizal 

 host previous to ascocarp formation. He found that sapro- 

 phytic fungi grew readily on culture media, but this was not true 

 of mycorhizal forms associated with certain trees in a symbiotic 

 relationship. 



An illustrated article by Hartley and Hahn on the diseases of 

 the quaking aspen, probably the most widely distributed tree of 

 our American forests, appeared in Phytopathology for March, 

 1920. After a discussion of fungi attacking the leaves, twigs, 

 and trunk, the authors conclude with the following summary : 

 " Observations have shown quaking aspen in certain areas to be 

 unusually subject to disease; trunk cankers of unknown origin 

 seem to be especially important factors in shortening the life of 

 the trees. Fomes igniarins is also an important factor in causing 

 premature death of aspen in the Pike's Peak region. Interesting 

 but less important diseases are (1) a twig blight suggesting' in 

 appearance the fire blight of pear; (2) a leaf disease due to 

 Sclerotium bifrons, E. & E., distributed from the Rocky Moun- 

 tains to New England and also attacking Lombardy poplar but 

 not Populus grandidentata; and (3) a rapidly spreading bark 

 trouble which kills cuttings." / 



A widespread leaf-spot disease of the German Iris caused by 

 Heterosporhim gracile, or Didymellina Iridis, is discussed at 

 length by W. B. Tisdale in Phytopathology for March, 1920. 

 This disease seems to occur wherever the susceptible, broad- 

 leaved species of Iris are grown, having been reported from 

 Wisconsin, New York, California, England, and elsewhere. The 

 fungus overwinters in the mycelial stage in the dead leaves. 

 Perithecia develop early in the spring, but do not always produce 

 asci, apparently on account of the weather conditions. Sterile 

 perithecia bear conidia on the apex. An abundant crop of coni- 

 dia, always present early in the spring, serves as the chief source 



