4 BULLETIN 684, U. S. DEPARTMENT OF AGRICULTURE. 



many weeks and even months, but when once suspended in water sub- 

 sequent drying kills them. These observations have several times 

 been confirmed by the writer. 



The ascogenous stage (PI. I, figs. 1, 2, and 3) is not very easily 

 found in nature or, if found, is rather difficult to identify, owing to 

 the frailness and consequent evanescence of the asci. Clinton (6) in 

 1902 and Von Schrenk and Spaulding (12) in 1903 succeeded in find- 

 ing it in diseased fruits and cankers, respectively. The writer has 

 also found this stage in bitter-rot mummies, in cankers caused by 

 the bitter-rot fungus, and in cankers caused by other agencies. 



SOURCES OF INFECTION. 



MUMMIED FRUITS. 



The mummied or rotten fruits which have remained upon the tree 

 or upon the ground since the preceding autumn constitute one of the 

 most important sources for the infection of the fruit of the current 

 year (PL II, fig. 1). Often, especially in the eastern United States, 

 they are by far the most important means by which the fungus is 

 carried over from one season to another. 



Clinton (6) in 1902 showed that the fungus could live through the 

 winter in mummied fruits. He states — 



However, in the fall and succeeding spring on the mummy apples, the fungus, 

 as a saprophyte, gives rise to the permanent or Gnomoniopsis (Glomerella) 

 spore stage. The Gloeosporium spores that have not been carried away disap- 

 pear through germination, and more or less of a mat of fungus thread covers 

 the apple. Protected by this, perithecia that develop asci, with ascopores, 

 which evidently came to maturity the next summer, are gradually developed 

 in a stroma. These ascospores are shed out of the asci and perithecia when 

 mature and are then scarcely to be distinguished from the Gloeosporium spores. 

 No doubt they are carried by the pomaceous flies to the green apples and thus 

 start the disease again for another year. 



As recorded by Burrill and Blair (4), Hasselbring did not find the 

 second spore forms, described by Clinton, on mummied apples kept 

 out of doors, but he found that the fungus ordinarily retains its 

 vitality in a dormant state in winter, and in May or later under 

 proper conditions begins to produce again the same kind of spores, 

 borne on fertile threads of the fungus, in the same manner as it did 

 the preceding summer. Spores secured from old mummies were in- 

 oculated into green apples and produced typical bitter-rot spots. 

 This was repeated with spores from bitter-rot mummies collected in 

 different orchards, and was found to be an easy procedure. Burrill 

 and Blair add — 



The spring infection may therefore start from these old apples, and recent 

 observations in the field have given indisputable evidence that it does sometimes 

 so occur. 



