1899.] PUBLIC DOCUMENT — No. 33. 157 



tions ; and, in order to ascertain whether the trouble with 

 which we were concorned was the same which he had briefly 

 alluded to, we forwarded him specimens for examination, 

 which resulted in establishing the identity of the two. 

 There is a certain resemblance ltd ween the spots which give 

 rise to bronzing and (hose which are caused by the black 

 spot; and we found that the impression prevailed among 

 some rose growers that bronzing was simply an immature 

 stage of the black spot. To any one thoroughly familiar 

 with the characteristics of both diseases, the differences be- 

 tween them would be evident, and they would not be likely 

 to confound one with the other. 



The investigations of Mr. Montgomery showed that the 

 abnormal condition of the rose leaves subject to bronzing 

 was not in anyway connected with fungi, but is of a physio- 

 logical nature, or structural weakness, as Professor Halsted 

 had correctly surmised. The first symptoms are manifested 

 in a mottled, bronzing coloration of the leaf. These spots 

 subsequently become more prominent, ranging from one- 

 sixteenth of an inch to one inch in size ; the infected por- 

 tions of the leaf frequently turn yellow, and eventually the 

 leaflets and leaf stalk drop to the ground. Sometimes, how- 

 ever, a whole leaflet becomes bronzed, and the yellowish 

 color is not observed. Numerous microscopic cross-sections 

 made of the bronzed leaf spots showed that the epidermal 

 and adjacent cells were in an abnormal condition. The 

 living contents of the cells were disintegrated, the proto- 

 plasm and cell walls had turned a reddish-brown color, and 

 numerous very minute bodies about the size of micrococci 

 filled the affected cells. These minute bodies proved upon 

 examination to be crystals of calcium oxalate. The exces- 

 sive deposits of calcium oxalate indicate that the leaf cells, 

 being unable to obtain sufficient nourishment, were not able 

 to assimilate the calcium salts, and consequently it is de- 

 posited in the cells in the form of calcium oxalate. It may 

 be said that all of this phenomenon is nothing extraordinary, 

 but merely concomitant with the death of the leaf, and can 

 be observed in other species of plants. Mr. Montgomery 

 states that the bronzed leaves are more susceptible to disease, 



