106 PRACTICAL FLORICULTURE. 



we are inclined to think it will hardly be retained as a first- 

 class forcing rose. 



The greatest pest wd have to contend with in Rose cul- 

 ture is mildew. Opinions as to its cause are varied and 

 contradictory. The theory is that mildew being a fun- 

 goid growth the seeds of which are ever present in the 

 atmosphere, when a relaxed condition of the plant en- 

 sues the minute seeds find a suitable place for their devel- 

 opment in the enfeebled leaf. Therefore we believe that 

 any thing that impedes the flow of the sap places the 

 plant in that condition fitted to develop mildew. Thus 

 vre often see our Roses without a taint of mildew during 

 all the winter and early spring months, until the hot, dry 

 days of the middle or end of May dry the soil in the pots 

 to such a degree that the plant wilts the sap is impeded, 

 and mildew follows. Or a door is left open and the frosty 

 air fastens on the stems and leaves, congeals the sap, enfee- 

 bles the plant, and though from an entirely opposite 

 cause, the result is the same. 



I once had a most marked example of this kind. Early 

 in April, we had an old-fashioned lean-to green-house 

 filled with Roses in full leaf, in the very highest state of 

 vigor. The house was some sixty feet in length and was 

 ventilated by sliding down every alternate sash at the top. 

 In ventilating on one occasion, the sashes had been neg- 

 lected until so late in the evening that the Roses exposed 

 to the air had become chilled by frost so that the young 

 shoots hung down as if wilted ; as the green-house got heat- 

 ed up they recovered, and to all appearance next morning 

 looked none the worse for being frozen ; but in a week 

 after, mildew appeared in a clearly defined square space of 

 about 3x3 fet, following almost exactly in the line where 

 the plants had been frozen. 



Had the sap been arrested by the roots getting dry in 

 that condition of growth, no doubt the result would have 

 been the same. 



