THE PRESIDENT'S ADDRESS. 59 



a very delicate bloom, caused by the fruit of the fungus 

 appearing on the surface. The young shoots also become 

 more or less swollen. As the mycelium of the fungus is 

 perennial in the shoots, and advances with each year's growth, 

 from whence it passes into the young leaves, the most certain 

 cure is to prune all diseased shoots and burn the same at 

 once. Even with this precaution, infection may occur the 

 following season from spores that have passed the winter in 

 crevices of the bark, etc. ; hence it is advisable to spray, just 

 when the leaf-buds are expanding, with dilute Bordeaux, 

 mixture. 



The leaves of apple-trees and plum-trees are often curled 

 inwards, variously distorted, and reddish in colour, due to a 

 disease which might at first be mistaken for leaf-curl. On 

 unfolding a leaf, however, the true cause of the mischief is 

 seen to be due to plant-lice, or aphides, which will be found 

 in various stages of development. In this case, spraying with 

 one of the many insecticides on the market will be necessary,. 

 and this should be done on the first symptoms of the disease,, 

 as when the leaves are compactly curled the solution does not 

 reach the aphides. • 



Mildew 7 . 



This name covers diseases produced by various species of 

 Ert/siphe and allied forms, all of which are characterised by 

 the formation of a white cobweb-like felt on the surface of 

 the foliage of various plants, as hops, peas, vegetable-marrows, 

 etc. When the disease is abundant the leaves present the- 

 appearance of having been whitewashed. 



In the majority of kinds of parasitic fungi the mycelium or 

 vegetative portion of the fungus grows in the tissues of the- 

 host-plant, the fruiting portion only bursting through to the 

 surface for the purpose of securing the dispersion of the spores.. 



