34 



BOTAXICAL GAZETTE 



[JULY 



marked effects entered: (a) swelling back of the root tip, and 

 lb) turning and coiling of root (fig. i); (3) concentration 1:40; 

 growth in length greatly retarded, also considerable swelling; 

 coiling present, but the coils smaller and tighter. 



With ethylene. — (1) Concentration 1 : 100,000 (that is, corre- 

 sponding to ethylene of illuminating gas with (1) above); appar- 

 ently no effect; normal growth ensued; (2) concentration 1 : 10,000; 

 responses similar to those shown in fig. 1 but somewhat more 

 pronounced; (3) concentration 1:1000; little or no growth in 

 length; strongly swollen, no coils. 



The parallel experiments with ethylene gave some evidence 

 that the toxic effect recorded for the illuminating gas may be due 

 to ethylene present in that gas because corresponding concentra- 

 tions of illuminating gas and the 

 ethylene-air mixture gave quite 

 parallel results. 



1. — Outline of Vicia Faba 

 roots, showing the effects of illumi- 

 nating gas on growth; A, control. 



2. With entire plants 



Material, radish, mustard, and 

 tomato. The roots and hypo- 

 cotyls gave responses as follows : 



Radish. — Exposure period 48 

 hours. 

 With illuminating gas. — (1) Concentration 1:500; bending of 

 root evident (similar to those of fig. 1); no coiling; no swelling of 

 hypocotyl or root; (2) concentration 1:5000; coiling and bending 

 of root evident; no enlargement of hypocotyl or root. 

 Mustard. — Exposure period 48 hours. 



With illuminating gas. — (1) Concentration 1:100; coiling and 

 bending of root evident (similar to those of fig. 1 ) ; swelling of hypo- 

 cotyl evident; no swelling of root; (2) concentration 1:11,000; 

 bending of root slight; no other effect; (3) concentration 1 : 20,000; 

 bending of root slight; no other effect. 

 Tomato. — Exposure period 3 days. 



With illuminating gas. — (1) Concentration 1:500; swelling 

 between stem and root (fig. 2); growth considerably retarded; 

 (2) concentration 1:10,000; swelling as above, but less marked; 



