196 MAIX^ AGRICULTURAL EXPERIMENT STATION. I909. 



fungus with which the apples were inoculated. Material from 

 the apple shown in Fig. 24 was fixed, sectioned, and stained 

 and the photomicrographs shown in Figures 39, 40 and 41 were 

 made from sections of the pycnidia. 



When this fungus was grown on prune agar, in petri dishes 

 the mycelium spread rather rapidly and in a few days had 

 spread over the entire surface. Considerable white aerial myce- 

 lium was i^roduced. When the cultures were a few days old, 

 little masses of closely interwoven hyphse began to appear which 

 were arranged in concentric circles. These gradually increased 

 in size and later drops of clear liquid exuded from them. The 

 appearance of the fungus in plate cultures is shown by Fig. 38 

 which is from a culture 11 days old growling on prune agar 

 from a piece of the decaying apple described above. At first, 

 it was thought that the little masses of hyphse were early stages 

 in the development of pycnidia but repeated examination failed 

 to confirm this as no bodies resembling pycnidia and no spores 

 were found. 



The mycelium consists of hyphae 5-7 microns in diameter 

 which in plate cultures radiate out from the center giving off 

 finer branches. The closely interwoven network made up of 

 the finer branches includes hyphse some of which are less than 

 2 microns in diameter. The length of the cells varies from 10 

 to 35 microns in the large hyphse but terminal cells 50-60 

 microns in length have been seen in the small hyphse. 



The fungus has been grown on only a few common culture 

 media. The growth on bean agar is very similar to what has 

 been described for prune agar. On sterilized bean pods, the 

 growth is good. The whole bean pod becomes covered by the 

 mycelium and a fine, white, cob-webby serial mycelium develops. 

 After the fungus had been grown for several months on bean 

 pods, the transfers being made each month, it began to produce 

 pycnidia. The pycnidia here had very much the same appear- 

 ance as those on the apple shown in Fig. 24. In some cases the 

 pycnidia develop singly and in other cases 2-4 pycnidia 

 develop in a sort of stroma. They always extend above the 

 substratum and are usually covered by fine white hyphse. 

 When the pycnidia are mature, the spores exude through an 

 opening at the apex and adhere together in long chain-like 



