\V. MCRAE 24S 



on the sides, while the fruits in the other two dishes were kept as checks. On 

 the 3rd day distinct discoloration began to show on most of the inoculated 

 fruits and next day was present in all. On the 5th day the spots had extended 

 (on one of them to 1| centimetres), and hyphae were present on the surface. 

 One of the fruits inoculated at the stalk-end had a spot of Penicillium and was 

 removed. On the 7th day the discoloration had extended well round the 

 fruit on most and entirely round on some. They were all sectioned and hyphse 

 of PhytophtJiora were f(tund in the mesocarp and endosperm, and the sporangia 

 on the outside were exactly like those of the Phytophthora in culture. The 

 control fruits were not discoloured. 



(6) The same experiment was repeated except that in this case the potato- 

 dishes were made into moist chambers by seaKng the two dishes with a water 

 layer. By the evening of the day following the inoculation discoloration 

 appeared on a few and next day was distinct on all. On the 3rd day it had 

 extended from 1 to 2 centimetres and hyphse appeared on the surface. On 

 the 4th day discoloration had reached half way round the fruit in most cases 

 and copious mycelium was present. On the 5th day 8 fruits were entirely 

 discoloured and 4 were almost so. In 5 of the fruits the mesocarp split along 

 the sutures and contracted slightly. Seven of the 8 control fruits were healthy 

 and one had a small spot of Fvsarium. The inoculated fruits were sectioned 

 and hyphae of PhytopJithora were found within the mesocarp which was soft 

 and sodden as in the fruits in nature. Hyphse were also found within the 

 endosperm and in the axis of the fruit-stalk. The sporangia corresponded 

 in characters with those of the culture. The control fruits did not become 

 rotten. 



{(■) In another experiment four fruits in a moist chamber were inoculated 

 by placing a drop of water, containing zoospores only, in the depression at the 

 stalk-end filled with water. Four other fruits were kept as controls. The 

 zoospores were got by allowing the sporangia on a piece of mycelium 

 on a slide to discharge freely, then carefully running oft" the water on to a 

 cover-sUp and transferring it to the water on the fruit. Three of these became 

 well infected by the 5th day and were examined when hypha) were found in 

 the mesocarp as well as hyphse and sporangia on the surface. The other was 

 uninfected, and the 4 control fruits remained healthy. The fungus can thus 

 infect the fruit at any part of its surface. Seeing that the infection of fruits 

 was used to test the infective capabihty of cultures made from various parts 

 of the plant, it was found in many trials that infection was more often successful 

 at the stalk-end as the depression roimd the insertion of the stalk holda water 



