182 American Gooseherrji-Mildew 



closely adjacent to these mildewed berries. Nine of these shoots were 

 microscopically examined, but no perithecium containing a living ascus 

 was found. In the majority of cases the ascus was empty and shrivelled ; 

 in the few cases where ascospores occurred, the ascus was not turgid, 

 and the spores were full of oily contents and evidently undergoing a 

 process of degeneration. In a very few cases the perithecium contained 

 the spores of the parasitic fungus A)npelomyces quisqualis {Cicinnobolus 

 Cesatii), but it was clear that the mildew had not been parasitised to any 

 appreciable extent. With regard to the bushes generally, the mildewed 

 berries were found either on branches from which all the young wood 

 (which had probably been diseased) had been cut away, or on spurs 

 on quite old wood. 



Since there is no evidence that in these cases these primary infections 

 had been caused by ascospores from the " over wintered " material 

 still present on some of the shoots, the explanation must be looked for 

 in another direction. There are two ways by which infection by asco- 

 spores could have occurred. As I have pointed out^, perithecia may 

 begin to fall to the ground in August from infested berries and, to a less 

 extent, from infested shoots. With regard to this particular plantation, 

 all the berries (as noted above) became very badly infested ; they were 

 not removed by the grower until late in August — by which time not only 

 must thousands of perithecia have fallen to the ground, but many of 

 the infested berries had fallen or been scattered by birds ; there must 

 therefore have been a heavy infestation of the soil. If, however, the 

 primary infections which were taking place in May had been caused by 

 ascospores arising from the soil, one would have expected to find the 

 majority of the mildewed berries on the lower branches of the bush, 

 ivhich tvas certainly not the ease ; the infected berries being nearli/ always 

 on the u])per branches. 



The second way by which infection could have been caused is as 

 follows. The " tipping," i.e. the removal of the infested shoots, was not 

 done until the end of October or beginning of November ; by this time 

 a considerable mass of perithecia must have dropped from the perithecial 

 patches. Many of these perithecia would doubtless lodge in the crevices 

 of the bark, or between the bud-scales, etc., and assuming that these 

 perithecia were mature ones capable of remaining dormant through the 

 winter, these would on liberating their ascospores infect the adjacent 

 berries. This theory, to which on the whole I incline, would account 

 for the fact that the berries in the upper part of the bush were first 

 attacked. 



1 Journ. Agric. Set., vi, p. 187 (1014). 



