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This is probably the commonest and most troublesome disease of 

 cultivated roses, whether of out-door or greenhouse cultivation, in 

 both Europe and America. It first appears in the form of dark dis- 

 colorations of the upper surfaces of the leaves, which spread outward 

 and often show a yellow band surrounding the dark spot. Often 

 the discoloration begins at the tip of the leaf and spreads downward. 

 The centres of the spot frequently become dry and brown, indicating 

 the complete death of the tissue. In consequence of the attack of 

 the fungus, the leaves fall from the stem and may be replaced by a 

 new crop if the weather be favorable. The loss of the functional 

 activity of the leaves at a time when their work is most needed, not 

 to mention the waste involved in producing an extra investment of 

 foliage, must greatly weaken the plant and lessen the amount and 

 vigor of its bloom, as well as seriously impaii- the ability of out-door 

 roses to resist the following winter. 



The mycelium of the fungus develops in the leaf, chiefly just below 

 its surface layer or cuticle. From this principal mass threads pene- 

 trate deeper into the interior of the leaf and absorb its fluids for the 

 nourishment of the fungus. Other threads grow upwards and 

 produce the spores, which, as they grow, make room for themselves 

 by forcing up the cuticle, which finally bursts open, allowing the ripe 

 spores to escape through ragged openings. The spores germi- 

 nate promptly on a moist surface, and readily infect fresh leav^. 

 It is probable that this parasite of the rose is merely an imperfect 

 stage in the life-history of a fungus, whose perfect stage is very 

 probably, or at least possibly, saprophytic and serves an important 

 purpose in carrying it through the winter. In the lack of definite 

 knowledge on this subject, however, we can deal only with the para- 

 sitic or Actinonema form. 



In combatting the disense it is essential to begin early, for leaves 

 once penetrated by the mycelium of the fungus are irretrievably lost. 

 All efforts must be directed toward preventing infection, by the 

 application of some protective compound. For this purpose it is 

 recommended that the bushes be sprayed shortly before the unfolding 

 of the leaves, again as soon as they are fairly opened, and at intervals 

 of three or four weeks until the flowers begin to open, especially 

 after heavy rains which may wash off the protecting substance from 

 the leaves, with blue-water or Eau celeste, prepared as follows : 

 Dissolve 1 pound sulphate copper 

 in 4 gallons warm water ; 

 when cool, add 1 pint commercial ammonia, 

 and 18 oallons water. 



