20 PAEASITES BELONGING TO THE GENUS GLOMEKELLA. 



area gradually spread toward the tip until the entire leaf was affected, 

 as illustrated in Plate VI. At other times acervuli broke out almost 

 simultaneously on the entire surface and were equally numerous both 

 on the upper and under sides of the leaf. On March 25 all but the 

 present year's leaves, which were not entirely discolored, were cov- 

 ered with the fungus. Small patches of mature perithecia were also 

 present. Though kept until April 13, the young leaves showed no 

 trace of acervuli or perithecia of Glomerella. 



On April 30 two more apparently healthy leaves were taken from 

 near the tip of a shoot bearing fruit one-half inch in diameter. These 

 were sterilized and placed in moist chamber, and two leaves from the 

 previous season's growth on the same branch were treated in the 

 same way. On May 7, acervuli were abundant on the older leaves. 

 On one, development was chiefly along the midrib; on the other, 

 chiefly along the margins. The younger leaves showed no acervuli. 

 On May 1 1 one of the younger leaves showed discoloration and a few 

 acervuli at the base of the midrib. The other young leaf showed 

 discoloration at the base, but had developed no acervuli on May 13 

 when the leaves were discarded. 



On May 11a young sterile shoot — that is, a shoot without a fruiting 

 bud — was taken from a greenhouse plant and the surface thoroughly 

 sterilized as usual. It was then cut into six segments, each one bear- 

 ing a single leaf. Each segment was placed in a separate sterile 

 moist chamber. This experiment was performed to determine 

 whether the fungus was equally abundant in fruiting and nonfruiting 

 shoots; that is, whether the fungus might possibly enter the flower 

 and gradually work back into the older parts of the shoot and foliage. 

 These segments were numbered 1 to 6, beginning at the basal end. 

 On May 18 all six leaves were more or less discolored, numbers 1 to 4 

 less than the others. In all cases the discoloration spread from the 

 base of the leaf toward the apex. All but No. 2 bore acervuli. On 

 May 27 all the leaves were entirely discolored and almost covered 

 with acervuli. The portions of the stem also showed acervuli. 

 Since leaves 5 and 6, which were near the apical end of the shoot and 

 youngest, became discolored slightly sooner than the older ones, it 

 might, perhaps, be inferred either that they were infected earlier or 

 that the tenderer tissues furnished more favorable conditions for 

 rapid development. 



On May 11 an apparently healthy fruiting shoot from the green- 

 house was sterilized as usual and cut in segments which were placed 

 in separate sterile Petri dishes. These segments were numbered 1 

 to 15, beginning at the basal portion of the shoot, as indicated in 

 figure 1. 



On May 18 the leaf on segment No. 1 was almost entirely covered 

 with acervuli. The portion of the stem to which it was attached 



252 



