are quickly conveyed by wind, rain, birds, insects, &c., to 

 neighbouring plants, and, unless drastic measures are 

 resorted to, an epidemic is the result. It is not necessary 

 to dilate on the difficulty experienced in checking an 

 epidemic of mildew. 



From the above brief account it may be gathered 

 that infection has taken place, some time before its 

 presence is revealed under the familiar form of mildew 

 or rust, and it is obvious that the prevention of infection 

 is the point to be aimed at. 



To effect this object two conditions are absolutely 

 necessary, viz., cleanliness and spraying. 



The cleanliness necessary is of a special nature. 

 The spawn or mycelium of many kinds of parasitic 

 fungi are perennial in the tissues of the plant attacked ; 

 in other words, when a plant is once infected the 

 mycelium remains in a living condition in the plant 

 from one year to another, and each season the disease 

 shows itself without any further infection from without. 

 This, however, is not the case with mildew, rust, and 

 black spot, the three most destructive and frequent of 

 diseases to which Roses are subject. During the winter 

 a given Rose tree, however seriously it may have been 

 attacked by either or all of the diseases named during 

 the summer, is perfectly free from disease, and will 

 remain so unless a new infection takes place. In the 

 case of mildew, infection is due to the winter spores 

 that are produced on the patches of white cottony 

 mildew growing on the shoots. The special cleanliness 

 in this instance consists in carefully removing every 

 trace of white felted mildew from the shoots and stem. 



