180 THE BOOK OF THE ROSE CHAP. 
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 Rose-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 thejuices. The leaf may thus be said 
to be suffocated and bled to death at the same time. 
