IX PESTS 179 



Cranston's book on Eose 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-glazed 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 O'idium 

 leucoconium in its summer and Spharotheca 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 



