104 TWELFTH REPORT. 



ANOTHER OBlr^ERVATION ON SCLEROTINIA FRUCTIGENA. 



J AS. B. POLLOCK. 



The question as to whether the brown rot fun^ns of the stone fruits, 

 Selerotinia fructigena, produces its asoocarps more than a ye^ir after 

 the mummied fruits have fallen from the tree has up to the present 

 been an open one. When Norton in 1902 discovered the ascocarps of 

 this species, he believed that they grew from mummied fruits which 

 had lain under ground two years, but this could not be demonstrated. 

 An opportunity has been presented to the writer to make the demon- 

 station that, this fungus does produce ascocarps the second season 

 after the mummied fruits have fallen from the tree. In the spring of 

 1909. on ground belonging to the Botanical Garden of the University 

 of Michigan, a group of plum trees was cut down before the leaves came 

 out. In preceding years these trees had borne regular crops of fruit, a 

 portion of which was always attacked by the brown rot fungus, Scleroti- 

 nia fructigena. The gTouud on which these trees stood was not culti- 

 vated and the mummied jjlums had fallen in the grass under them for 

 years, some of them being covered with earth througli the action of earth 

 worms and the washing action of rain. No other plum ti'ees stood 

 within thirty rods of the trees under consideration, and the conditions 

 were thus favorable for determining the question whether the mummied 

 plums, or rather the sclerotia contained in them, would develop the cup- 

 like ascocarps more than two years after they liad fallen from the tree. 

 In 1909 a good collection of the ascocarps was made where the plum 

 trees had stood, and again in 1910. The apothecia were growing di- 

 rectly from the old mummied plums, which had fallen from the trees not 

 later than 1908. This demonstrates that two-year-old mummies are 

 capable of developing ascocarps. Reade reports that in his work on 

 Solerotinia he obtained the apothecia in about a year in artificial 

 cultures. 



In another species, Sclerotinia' aestivalis, Avhicli the writer described 

 in the Michigan Academy Report for 1909, mummied apples collected 

 in the summer of 1908 produced ascocarps all through the summer of 

 1908, and after standing over winter dry in the laboratory in covered 

 glass dishes which had served for moist chambers, the same mummied 

 apples produced another crop of apothecia in April 1910. The second 

 crop was decidedly smaller in size than the first one of the preceding 

 summer. It developed after the apples had again been moistened, and 

 kept in the moist chamber. 



It is certain then that not only can sclerotia of Sclerotinia produce 

 lascocarps two years after the sclerotia were first formed, but also that 

 in at least one species of Sclerotinia the same sclerotium can produce 

 two crops of ascocarps. Whether the last statement is true of Sclero- 

 tinia fructigena we do not know, but it seems not improbable. The 

 ability to produce ascocarps the second year whether they are the first 

 or second crop from a given sclerotiuuL must be of considerable im- 



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