182 THE BOOK OF THE ROSE CHAP. 
stems. In such places, and especially on the leaves 
which are now fallen, the mildew seeds have retired 
to rest for the winter, and no frost or cold, drought 
or moisture, can harm them. 
These winter places of retreat are tiny black spots, 
only visible on the dying leaves by the aid of a 
magnifying glass, though a higher power of the 
microscope reveals them as round black receptacles 
or boxes, each containing eight spores. In these 
minute black spots on the leaves Rose mildew 
passes its winter sleep, unhurt by all that may 
befall, save fire or being buried deeply in the ground. 
The sun of the following summer will burst the 
walls of the cases, and set free the spores once 
more. 
Collecting and destroying by fire the fallen leaves 
is thus plainly the only mode of prevention, which 
in most cases will probably be found impracticable, 
but even a partial carrying out of this plan should 
have some effect. It is impossible to say how far 
the spores may be carried by a strong wind, but 
probably many miles. An actual stamping out of 
the pest is therefore, I fear, beyond our reach. 
Preventive measures consist first in the choice of 
an open situation: in a confined place the seeds 
floating in the wind are more apt to drop, or to be 
carried round and round till they do attach them- 
selves to the leaves: where there is free passage for 
the air, the same wind that brings them will take 
most of them farther on, and only a few will find 
resting places. 
Against harmful seeds brought by the wind, there 
are therefore two preventive measures : either abso- 
lute exclusion from any wind or even air, or entire 
