180 THE BOOK OF THE ROSE cjiap. 



The spores or seed are set free from their winter 

 resting places by the heat of early summer, and 

 float in the air, some at least commencing to 

 germinate and throw out roots even before they 

 alight. Like other parasitical fungi-spores, a certain 

 condition of the atmosphere and also of the leaves 

 on which they fall is necessary for the actual 

 development of the fungus growth ; when these are 

 present the first visible sign is a spot or curl on a 

 young leaf, which is raised or depressed according 

 as the mildew has attacked the upper or under 

 surface. 



It should be noticed, as an important thing to 

 remember, that the mildew is always worst on the 

 under side of the leaf, and is often found there 

 alone. For this at once puts aside as useless the 

 merely dredging the affected parts with sulphur, as 

 this cannot touch the worst places; and it is 

 evident that it must be puffed from below as well 

 as from above, and that in all syringing with liquid 

 the under surfaces of the leaves must have even 

 more attention than the upper. 



The first thing the mildew spore does when it 

 begins to grow on the Bose-leaf, is to form the 

 mycelium — the tiny white threads which are com- 

 mon to all fungus growth from mildew to the mush- 

 room of the fields. This, when woven closely 

 together in masses, forms the spawn, and then the 

 white efflorescence is seen on the leaf. 



The leaf breathes through pores on the under 

 surface ; these are choked by the woven mass of 

 mildew spawn which also pierces the membranes 

 and lives upon the juices. The leaf may thus be said 

 to be suffocated and bled to death at the same time. 



