292 



INJURIOUS INSECTS AND FUNGI. 



[Dec. 1896. 



the hop mildew, shown by Fig. 1. These were very numerous 

 in some of the cones ; though indistinguishable by the naked 

 eye, they seemed to be little black groups which would be 

 taken for decay of the tissues or the blackness occasioned by 

 aphides. Under the microscope they appeared as the perithecia 

 of Podosphcera castagnei, and it was seen further that the 

 mycelial threads of this fungus were permeating the tissues of 

 the bracts of the cones, and by extracting their juices were 

 producing decay and consequent change of colour. 



Fig. 2. 



0 



A. Side view of a perithecium of Podosphcera castagnei, discharging ascus, B, 

 which is opening and discharging eight sporidia, C, x 200. 

 D. Conidiophore x 200. 



The fungus was seen in all its stages. The mycelium was 

 upon the bracts, and its branching filaments were within their 

 tissues, although the habit of this fungus is said to be epi- 

 phytic. Besides the haustoria there were evidently mycelial 

 threads within the epidermal cells. To make more sure of this 

 infected cones were sent to the Rev. J. E. Vize, who made some 

 minute transparent sections in which filaments of the fungus 

 were traced beneath the surface. 



From the mycelium, conidiophores, shown at D (Fig. 2), were 

 springing, white and glistening. These were not so abundant 

 as when formed upon the leaves and upon the incipient cones 

 earlier in the season, at which time they form thick white 

 congeries of mould, but they were clearly in evidence. 



At the eame time the perithecia, or spore cases, were 

 discharging asci, somewhat ovoid receptacles (B, Fig. 2), con- 

 taining eight ovoid spores, and plenty of empty cases were 

 found in the cones. It may be stated that as early as the 

 10th of July perithecia were found in the congeries of mycelium 

 upon hop leaves, so that there are two sources of infection, 



