156 HATCH EXPERIMENT STATION. [Jan. 



and more care should be exercised in their application. 

 Most fertilizer companies give explicit directions as to the 

 amounts which should be employed, and the excessive use 

 of them is generally traced to the carelessness of the 

 gardener in applying them. The results of over-feeding 

 generally manifest themselves in some abnormal stimulation 

 to the plant ; but these results, even when the same fertil- 

 izer is used, do not show themselves in a similar manner on 

 diflerent species of plants. What would give rise to a 

 multiplication of cells and the formation of blisters in the 

 leaf of one plant, would not do it in the leaf of another. In 

 short, stimuli in plants manifest themselves specifically and 

 manifoldly. 



The Bronzing of Rose Leaves. 



A peculiar bronzing or irregular spotting of rose leaves was 

 brought to our attention last winter by Mr. Alexander 

 Montgomery, Jr., a member of the senior class. This 

 peculiarity in the spotting or bronzing of the leaf is common 

 to grafted varieties of the Tea, Bride and Bridesmaid roses, 

 grown at the extensive Waban conservatories at Natick ; 

 and Mr. Montgomery, who was working in the botanical 

 laboratory at that time, made, at my request, some investiga- 

 tions into the cause of the trouble. Both Mr. Montgomery 

 and his father, who is in charge of the Waban conservatories, 

 have had ample opportunity to observe bronzing ; and it 

 therefore became a very easy matter to secure valuable data. 

 The only mention which we have noticed in connection with 

 this disease is that given by Professor Halsted of New 

 Jersey, who briefly referred to it in his annual report of 

 1894.* In this report he gives a figure of the black spot of 

 the rose, and in connection with it is shown what he desig- 

 nates a " discoloration that is most frequently met with on 

 the foliage of the La France, and may be called bronzing." 

 This he states, so far as he knows, is "not due to any 

 fungus, and is likely due to a structural weakness." This 

 reference to the disease by Professor Halsted was not ob- 

 served until Mr. Montgomery had finished his investiga- 



* New Jersey Experiment Station Report, 1894, p. 384. 



