ROSE DISEASES. 243 



prise. In four days from the time spores were introduced 

 into sterilised sections of rose twigs in test tubes, the 

 whole of the culture would be covered with the spore 

 masses. 



Eembdies. — Burning the infected bush is the only way 

 of stamping out this disease. 



Canker. — This is a disease which of late years has 

 proved exceedingly troublesome to growers of the Marechal 

 Niel rose. The lower part of the stem should frequently 

 be examined, and as soon as shrinkage or swelling is 

 observed, cut a little of the bark away to see if it is decay- 

 ing. The earliest form of canker is a shrinkage in the 

 bark, caused by some unknown disease, which keeps 

 spreading until it gets all around the stem, then the part 

 above it dies. But before this takes place, a swelling 

 of a warty appearance forms just above it; this is caused 

 by the descending sap being stopped in its downward 

 course; ifc seems to be trying to make a growth to cover 

 the wound, but, of course, cannot do so. 



Remedies. — All this knotty excrescence, also the 

 shrinkage, should be cut away, likewise all decayed w^ood 

 and bark; sometimes there will be dark narrow streaks 

 running some distance beyond, these must be followed 

 up until every portion is cut aw^ay. Then dress the 

 wound with either Bordeaux mixture, sulphate of iron, 

 two ounces dissolved in a gallon of water; or sulphide of 

 potassium one ounce to twelve gallons of water. If none 

 of these are at hand, rub the part well with flowers of 

 sulphur. After (whichever is used) make a poultice of 

 equal parts clay and cow manure and bind round the 

 wound. The summer is the best time for the operation, 

 as the wound heals over much more quickly then. 



Downy Mildew (Peronospora sparsa, Berk.). — Some 

 rose growei-s are troubled with a second form of mildew 

 which differs in many ways from ordinary mildew. It is 

 less easy to detect, and, being more deeply seated, may do 



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