Rose Mildew 



upon a leaf or shoot, when moisture, temperature, 

 and air - supply were suitable. It threw out a 

 minute thread from which, if it has reached a leaf 

 which the fungus is capable of attacking, suckers 

 are soon thrust out into the leaf-tissues in search 

 of food. 



Feeding on the sap it absorbs, the fungus gradu- 

 ally and quickly spreads all round the spot first 

 attacked and throws up a number of short upright 

 threads from the tips of which spores are pinched 

 off in great numbers. These give the mealy appear- 

 ance already alluded to. The spores are easily 

 carried to other spots, and if conditions are favour- 

 able spread the disease. 



These summer spores are produced in great 

 numbers as the parasite grows, but each lives 

 only a short time. Later in the season, when the 

 myceKum has formed a felt, another form of 

 spore is produced inside cases with resistant walls, 

 and these remain over winter, burst in spring, and 

 liberate the spores to renew the disease another 

 season. The felted mycelium may also remain alive 

 and form a centre of infection for another year. 



The fungus is the cause of the disease : the host 

 suffers from actual loss of food of which the fungus 

 robs it, and more still from the crippUng of the 

 foliage which prevents it from performing its 

 fimctions of food-making, etc., to the fullest extent. 

 But the host has, under certain circumstances, the 



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