Dec. i6, i9i8 Brown Canker of Roses 595 



limited, the cane being darkened and killed for a radius of about X inch 

 from the point of inoculation. A microscopic examination revealed 

 the presence of hyphae in the darkened tissue, but the fungus did not 

 fruit on the diseased area. Plantings were made in corn-meal agar 

 poured plates from small portions cut from the edge of the discolored 

 tissue with a sterile scalpel, then immersed in a mercuric-chlorid solu- 

 tion (1:1,000) for about three minutes, and rinsed in sterile water. In 

 such cultures made on January 19 the imperfect stage developed in five 

 •days, while cultures made similarly from the controls remained sterile. 



Inoculations with B were again made in the greenhouse on Janu- 

 ary 30. No infection resulted from two of the inoculations, which 

 may not have been kept sufficiently moist, but on February 13 it was 

 observed that the third inoculation had produced infection. Plant- 

 ings were made in April from the discolored region and from a corre- 

 sponding region of the control. The fungus was reisolated from the 

 inoculated plant, while no growth appeared in the culture made from 

 the control (Pi. 47, C, D). 



On January 17 freshly cut rose canes were placed under the bell 

 jars in the laboratory and inoculated %vith B. Infection appeared in 

 10 to 15 days from all of the inoculations. The progress of the dis- 

 ease may be described from the observations taken on one of the inocu- 

 lated canes, which when first observed was girdled and darkened for 

 I inch above the point of inoculation. In two days the disease advanced 

 upward 3 inches, and in three days the entire cane above the point of 

 inoculation was affected. The disease passed downward less rapidly. 

 An area, lighter in color and similar to that described in the A inocu- 

 lations, appeared near the point of inoculation. In this area the typical 

 pycnidia developed (Pi. 47, A, B). 



Two inoculations were made by smearing an infusion of spores of 

 stage B on the leaf buds. From each inoculation infection appeared at 

 the base of the bud in about 10 days, and the disease advanced for several 

 inches along the stem. The spores evidently germinated on the leaf 

 tissue, the fungus passing through the bud into the cane. This experi- 

 ment does not indicate that the fungus may gain entrance through the 

 healthy or uninjured buds, for in making the inoculations no precau- 

 tion was taken to avoid injuring the tender leaflets. 



These experiments ^ establish the pathogenicity of the fungus. The 

 percentage of infection appears to vary with temperature and humidity 

 as shown by the results of the different series of inoculations. Inocu- 

 lations made under bell jars gave 100 per cent infection, while those 

 made without covering the plants gave a smaller percentage of infection. 

 When the fungus is once established, it advances rapidly, producing 

 the characteristic lesions. 



' Subsequent to the writing cf this paper, the information has been received from Dr. L. M. Massey, 

 of Cornell University, that he has also made successful inoculations on roses in the greenhouse with 

 what appears to be the s^me fungus. 



