BOTANICAL GAZETTE 



[JULY 



and B respectively of rig. 6. Through an examination of figs. 5 

 and 6 it becomes evident that the stelar region has remained un- 

 changed, while the cortex, 

 extending to the phellogen 

 layer, has increased in 

 thickness, partly through 

 increase in the diameter of 

 the cells, and partly 

 through cell division. At 

 the phellogen layer of the 

 treated root, cell division 

 has been rapid, resulting 

 in the production of a 

 loose tissue not present at 

 all in the normal. The 

 tissue lying outside the 

 phellogen layer in the 

 beginning has been only 

 slightly modified in the 

 abnormal root. 



/) A number of tests 

 were carried out with 

 Gleditschia seedlings, used 

 in illuminating gas in 

 various concentrations up 

 to 1:3 (concentrations 

 higher than 1:3-1:4 were 

 not used for fear of oxygen becoming a limiting factor). Concen- 

 tration 1:3 gave leaf fall, but no definite injuries were detected in 

 the root system. 



2. Qualitative tests with potted woody plants 



When illuminating gas was passed rapidly through the soil of a 

 potted plant, injuries might be observed the first day and death 

 in all cases in the course of a few days. This is not at all surprising, 

 because one should expect injury and final death to result as an 

 effect of the shutting off of the oxygen supply, even though an 



Figs. 4, 5. — Fig. 4., section through the cortex 

 of tap root of Catalpa: A, control; B, treated 

 with illuminating gas; fig. 5, same for Ailanthus 

 roots, showing detail of the tissue regions out- 

 lined in fig. 6; X48. 



