88 Journal of Agricultural Research voi. xv, no. 2 



condition of cells recently found by Samuels ^ to accompany the process 

 of precipitation of raphides of calcium oxalate. 



Quite often in older intumescences there seems to be a return to the 

 meristematic condition in certain cells, so that a cambium-like layer 

 is formed which pushes out conical-shaped rows of cells to form the tumor 

 (PI. lo, A). After two weeks' growth the tumors begin to die back, and 

 infection may occur (PI. 10, B). Before this time no bacteria have been 

 observed in the formation of the tumor. 



Growth is sharply confined to the area injected and does not spread to 

 the other cells. Such limitation would hardly be the case if bacteria were 

 concerned in the growth stimulus. The growth is not due to any condi- 

 tion peculiar to the cabbages used, for identical growths have been ob- 

 tained during different years. Similar intumescences have been pro- 

 duced from frost-injured spots on the leaves of Bryophyllum calicynum. 



Small growths have also been observed to be produced from injected 

 areas on the leaves of lettuce and salvia. The cells of injected areas of 

 hardened cabbage leaves are not stimulated to growth by moderate freez- 

 ing. Since plasmolysis of the cells occurs in this case, as well as in the 

 cells of nonhardened plants, it appears that plasmolysis alone is not the 

 cause of the growth stimulus. 



Young intumescences contain large quantities of dextrose, much more 

 than the ordinary leaf cells. Levulose is present in only small quantities, 

 if at all. When heated with Fehling's solution, an abundant precipitate 

 of cuprous oxid is formed in the tumors, giving them a reddish color. 

 Starch and tannins are absent from the hypertrophied areas. 



PEROXIDASE CHANGES IN THE INJECTED AREAS OF CABBAGE LEAVES 



A lot of cabbage leaves were spotted and placed in the greenhouse to 

 allow the development of tumors. From time to time samples of the 

 spotted leaves were tested for peroxidase. Tetramethylparaphenylene- 

 diamin in 60 per cent alcohol was used as the reagent for oxidase, and 

 ID per cent of commercial hydrogen peroxid was added to this to demon- 

 strate the peroxidases. In these reagents the activity of the solutions 

 was tested on sections of potatoes on which known reactions were given. 

 Little or no reaction for oxidase was obtained in cabbage leaves within 

 the time in which potato sections gave a good reaction. This was sup- 

 ported by testing the leaf juices in the Bunzell (4) apparatus, which 

 showed comparatively little oxidase activity with tyrosin, pyrogallol, 

 hydroquinone, and pyrocatechin. It was found that with tetramethyl- 

 paraphenylenediamin a good test for peroxidase was given along the 

 veins of the cabbage leaf. In leaves tested immediately after spotting 

 no more peroxidase reaction was given in the injected than in other 

 areas; nor could any greater amount of peroxidase be demonstrated in 



1 Paper read before the American Association for the Advancement of Science, New York, 1916. 



