Exoascus insititise. 



This fungus is one of the most interesting of the parasitic 

 diseases which attack the genus Pntnus. The word " Exoascus " 

 has special reference to the shape of the hyphje, or aerial 

 portions of the fungus, which resemble in shape small bladders 

 or pockets. These, when fully developed, contain the spores. 



The fungus attacks the young fruit as soon as it begins 

 to swell ; the characters of the tissues are changed by the action 

 of the mycelium of the fungus, and a curiously malformed 

 development takes the place of naturally formed fruit. Some 

 specimens attain dimensions three and four times larger than 

 those of a normal-sized fruit. In this condition they are known 

 as " bladder-plums " or " pocket-plums." They are quite useless 

 for the purpose of food. The growth is completed in about 

 six or seven weeks, and very shortly afterwards they shrivel and 

 fall to the ground. A remarkable feature is that no stone or 

 kernel forms, the fungus diverting and absorbing the supplies 

 of nutriment that would otherwise have produced them. When 

 mature the skin is wrinkled, of a greyish or greenish colour 

 tinged and spotted with dirty yellow and orange, and having 

 a kind of bloom on it which is due to a dense covering of the 

 hyphse. 



The fruit shown in the opposite plate is that of the bullace- 

 tree. In the summer of 1900 several trees were growing on a 

 farm in Guestling which were very full of diseased fruit, many 

 clusters of five and six bullaces being attached to one twig. 



The illustration is of .specimens gathered at Guestling by the 

 author. 



