Apr. IS, 1915 Apple Bitter-Rot 63 



the spores from this source were comparatively few, they were, never- 

 theless, sufficient to give the disease a good start. In the same orchard 

 an occasional fruit spur was found from which spores were somewhat 

 sparingly produced after it had been kept in a moist chamber for from 

 24 to 48 hours. The part from which the fungus was obtained was the 

 dead tip on which the fruit of the preceding year had been borne. 



In at least two well-authenticated cases acervuli were found on the 

 injured parts of small limbs which had been nearly girdled by the organism 

 of pear-blight {Bacillus amylovorus) . These cankers had been caused by 

 the blight organism infecting and killing a small twig and going thence 

 into the tissues of the limb at the base of the twig (PI. VII, fig. 4). 



In one orchard which had been badly infected for years it was possible 

 to find the fungus on almost any sort of cankered or injured limb. From 

 directly above a mass of badly infected apples still hanging on the tree, 

 a small limb having a long dead area just beginning to be healed over 

 through the formation of callus was removed (PI. VII, fig. 5). This 

 injury had apparently been brought about by mechanical means; prob- 

 ably the limb had been severely scraped by the tower of a power sprayer 

 or by a wagon box or hayrack, all of which were accustomed to pass 

 through the orchard at frequent interv^als. After a short time in a moist 

 chamber acervuli appeared from beneath narrow strips of dead bark 

 which lay near the angle formed by the dead area and the overlapping 

 callus. This injured area was 19 cm. long and 4 mm. wide and contained 

 innumerable acervuli. That this mechanically injured limb had served 

 as a source of direct infection was indicated by the fact that there were a 

 large number of badly infected fruits just below it, whereas all the apples 

 above it were sound. No other possible sources of infection were present. 



This orchard was also badly infected by the apple-blotch fungus 

 {Phyllosticta solitaria). The cankers caused by this organism were 

 quite numerous on the smaller limbs and branches, especially in the 

 older part of the orchard which had been practically abandoned. In 

 connection with some work with the apple-blotch fungus the writer 

 had occasion to scrape from these cankers (PI. VII, fig. 6) spore-bearing 

 pycnidia of Phyllosticta solitaria, which, after being crushed, were placed 

 in Van Tieghem cells so that spore germination might be observed. 

 In many cases bits of bark were accidentally carried into the Van Tieghem 

 cells along with the pycnidia and spores of the blotch fungus. Repeat- 

 edly during the month of May and later as well there grew out from these 

 small bits of bark hypae which produced spores (conidia) of the bitter- 

 rot fungus. Cultures from these spores produced the characteristic 

 acer\mli and conidia and often the perithecia and ascospores of Glom- 

 erella cingulata. 



Masses of spores were also obtained many times from mummies ; and 

 where mummies are present, thev undoubtedly are important sources 



