226 'TEXT-BOOK OF FUNGI 



diseases are ' Apple-tree canker ' (Nectria ditissima), which 

 in its advanced stage is very conspicuous, but in its incipient 

 condition on young trees, such as are exported, it is very 

 doubtful whether its presence would be detected in a 

 cursory examination at the port of entry. 'Apple-tree 

 mildew' (Sphaerotheca mali) is very conspicuous on the 

 foliage, but if the foliage is not present it would not be 

 detected, but would certainly reveal itself when new leaves 

 appeared, as the mycelium of this fungus hybernates in the 

 branches. 



Much has been made of the recent appearance of the 

 American gooseberry mildew in Ireland. How was it 

 introduced ? No one knows, or, if they do know, do not 

 appear to be inclined to tell. The point is, Was it intro- 

 duced on living plants in its fully developed, conspicuous 

 condition, in which case it could not have escaped the eye 

 of an official on the lookout for diseases, or did it come 

 under the form of spores adhering to the plant, which in 

 due season produced the disease ? In the latter case no 

 official, however observant, could have detected its pre- 

 sence. To state that if legislation on the point had been 

 in force the disease would not have entered Ireland, is only 

 the expression of an enthusiast, and will not bear criticism. 



Another very destructive disease that has found its way 

 from one country to another is ' Peach leaf-curl ' (Exoascus 

 deformans). When the diseased foliage is present this 

 disease is unmistakable, but after the foliage has fallen the 

 tree shows no trace of its presence. Nevertheless the 

 disease is present, as the mycelium is perennial in the 

 branches, and would probably reveal itself the following 

 season. 



The importation of ripe fruit into a country is undeniably 



