SiLBERBERG : STIMULATION OF STORAGE TISSUES 



493 



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could be drawn with regard to them. The variability in the re- 

 sults, in this instance, was largely due to the presence of vascular 

 bundles running through the pieces used for experimentation. 



The presence of the vascular bundles also confused, somewhat, 

 the results obtained from salsify. In four cases out of seven, how-, 

 ever, when the control pieces and the poisoned pieces were cut as 



a* 



Figure 2, Transverse and longitudinal sections of cylinders of tissue from " kohl- 

 rabi " for comparison of extent of callus formation with and without stimulation by 

 zinc sulphate, a and c are the control specimens ; h and d were stimulated with N/12 

 zinc sulphate. The drawings represent the condition two weeks after cutting, the 

 stimulated specimens having been treated at once after the cylinders of tissue had been 

 removed. Magnified 3 diam. 



nearly alike as it w^as possible to make them, and always taken from 

 the same plant, the specimens dipped in tAvelfth- and fourteenth- 

 normal zinc sulphate solutions showed a greater formation of cal- 

 lus than the control specimens. In the other three experiments, 

 the stimulated specimens formed less callus than the control speci- 

 mens. In one of these three experiments, however, more meri- 

 stem had formed in the poisoned piece than in the controL 



In the experiments with the kohl-rabi, the same precautions 

 were taken as with salsify, because of the presence of bundles. 



