97 



At last these dark spots turn white, or at least ash-coloured, at the 

 centre, and this is an indication that the fungus, which is causing 

 the disease, is about to fructify or produce spores. The spores are 

 formed in very minute pustules that can be seen only with the aid of 

 a good magnifying glass, and yet so fertile are they that a single spot 

 of the disease may give rise to many thousands of spores, each capable 

 under proper circumstances of producing a fresh infection. 



The disease runs its full course in a few 

 weeks time, as may be readily ascertained 

 by examining the youngest leaves that 

 display full-grown spots. It is usually 

 the lower leaves on the plant that suffer 

 most severely ,f or the reason that through 

 the action of dews and rains an abundance 

 of spores are washed on to them from 

 above. Nevertheless, the highest leaves 

 are often found infested, a proof that the m> ._ Spore 7 of PhyllMa Rogarum 

 wind also plays an important part in the Pass., the cause of the Black spot of the 



-i , .-I .. ,-i Rose. The simple, smooth, colourless, 



distribution OI the Spores. ellipsoidal spores, measuring 5'-7'2 x 



The differentvarietiesof rose Yarycon- JttJZSS&Sn&S 



Slderably in their susceptibility to the pentheeia, about 100? in diameter, 



disease, and different plants of the same SeSlSSSSJffttfiTS 



SOrt Show Variations according to locality, midst of more or less circular spots found 



-, p,t -XT i on the upper surface of the attacked 



age, and SO forth. New gardens leaves, and characterised by a distinctly 



started from carefully selected cuttings, 

 and at a little distance from other roses, 

 may remain free from the disease for 

 some time. Some varieties appear almost never to suffer from the 

 disease, and these are particularly the small-leaved and climbing sorts. 

 The rank growing sorts, producing large and succulent leaves, are the 

 worst sufferers. This disease is readily distinguished from the other 

 common spot-producing disease of the rose by the fact that the diseased 

 areas are in the present instance never radiate or star-shaped. Moreover, 

 the spots of the " Star-shaped Leaf Spot" are very seldom so dark as 

 those of the present disease, though they are often much larger. (See 

 coloured Plate opposite p. 26.) 



Remedies. 1 . Foremost among the remedies must be placed hand 

 picking, which, if carried out watchfully, will in most cases be 

 sufficient. It is not sufficient to remove simply those leaves that show 

 black spots. The eye must be trained to see the beginnings of the 

 disease, and so become able to indicate what other leaves should be 

 destroyed. Where a few roses are grown as a recreation or for 

 ornament this is the method that will most commend itself. The 

 labour is not great, and will not be grudgingly bestowed where it is 

 being expended for love rather than for profit. 



2. Pruning is a more severe measure that may be resorted to in those 

 cases where the plants are much infested, and where it is desired to 

 reduce the disease at one stroke. As in the case of the plucking of the 

 leaves the parts removed had better be destroyed. 

 36567 G 



