PHYSIOLOGICALLY ACTIVE GASES 



161 



the stem and the control plant none. The results are Ulustrated in (A) con- 

 trol and (B) treated plant in Fig. 61. So far as the author knows, this was 

 the first time an effective root-inducing chemical was reported. Carbon 



Figure 61. Tomato plants treated with carbon monoxide gas. A, Control m Wardian 

 case for 11 days. B, Plant exposed to one per cent carbon monoxide gas for 5 days and 

 then held in Wardian case for 6 more days at the end of which time it was photographed 

 Note the slender root growth made after the plant was removed from gas. C, Control 

 plant. D, Plant with a flask of carbon monoxide sealed over a leaf. Note the epmastic 

 response of the leaves, indicating that the gas is taken in through the leaf and transmitted 

 to all parts of the plant. 



