158 HATCH EXPERIMENT STATION. [Jan. 



and he has observed the occurrence of rust upon them, while 

 healthy leaves would be entirely free. 



A further examination of the affected plants at the Waban 

 conservatories, made by Mr. Montgomery and myself, showed 

 that all leaves even of plants subject to it were not affected, 

 but that it was confined in every instance to two places : 

 first, where a stem is cut and a new branch starts, the leaf 

 at the base of the branch begins to bronze ; second, when 

 an eye or axillary bud is rubbed off, the leaf generally 

 becomes bronzed. 



There is a difference in susceptibility between young plants 

 and old ones. Roses planted in the middle of June show 

 bronzing the first of August, but it is scarcely noticed after 

 the first year's growth. Bronzing appears to occur more 

 largely upon plants which show rapid growth than on those 

 which have grown more slowly ; for this reason apparently 

 the root plants or ungrafted ones at the Waban conserva- 

 tories which are not so vigorous as the grafted ones are not 

 susceptible to it. Bronzing sometimes occurs upon small, 

 weak stock. 



It should be stated, however, that, since bronzing occurs 

 on leaves at the axils of the shoots which bear the flowers, 

 no real harm is done to the marketable foliage, as the cut- 

 ting of the flower stalk is always above the position of the 

 leaves which are bronzed. The most intelligent and suc- 

 cessful rose growers always take the most care and pride in 

 their plants, and they are suspicious of any abnormal feature 

 which in any way mars the beauty of them ; and this is, so 

 far as we have observed, the only inconvenience which this 

 trouble of bronzing gives rise to. 



It is quite evident that we have in the bronzing of rose 

 leaves a physiological phenomenon which is not uncommon 

 to other plants. We have observed a similar falling of the 

 axillary leaves in other species of plants. In the rose it is 

 probably a correlative phenomenon, which is brought about, 

 or at least augmented, by years of cultivation and develop- 

 ment along certain lines. Any form of mutilation, whether 

 it be a cut or a mere scratch, acts as a stimulus to a plant ; 

 but the manner of reaction of the plant may not always be 



