1X PESTS 179 
Cranston’s book on Rose culture, the first edition of 
which was published in 1855, that it was not 
so prevalent at that time as it has since become. 
The greatly increased culture, and the introduc- 
tion of varieties of weak constitution with soft 
spongy leaves, have probably been responsible for 
this. 
It is an error to suppose that stout thick leaves 
are proof against mildew : if soft and succulent these 
are often the earliest attacked. It is the hard shiny 
well-clazed leaves upon which the mildew spores 
can find no footing; and Teas, whose leaves are 
rather more of this character, do not generally suffer 
much from mildew, except under glass, till late in 
the season. 
Few indeed are the collections of Roses which 
now pass through a season without at least traces 
of this pest, though close and confined situations 
always suffer more than those which are open and 
exposed to free currents of the air. The amount of 
harm done will greatly depend upon the time when 
the mildew first makes its appearance. It is a bad 
look-out to see the first plague spots in June, for if 
war is to be waged it must be unceasing, as the 
enemy will constantly reappear when it has once 
shown itself. When well into July the buds will 
probably be sufficiently advanced to escape serious 
damage in themselves. 
The life-history of the fungus, called Oidiwm 
leucocontwm in its summer and Spherotheca pan- 
nosa in its winter condition, has been thoroughly 
investigated, a full and interesting paper on the 
subject having been published in the Rosarian’s 
Year book for 1886, by Mr. Worthington G. Smith. 
N 2 
