32 BOTANICAL GAZETTE [july 



then the roots and glass tubes were sealed in with a vaseline- 

 paraffin mixture by the Briggs and Shantz method. The total 

 volume of the interstices (allowing for a definite water content) was 

 previously determined, and upon the basis of this volume, known 

 concentrations of gas could be secured. The duration of experi- 

 ments was 5-21 days. Gases were changed every three days by 

 drawing pure air through the jars for 10-15 minutes by means of 

 an aspirator, and new gas added. Parallel experiments with 

 ethylene were also run in many cases. 



2. Qualitative tests 



In this series of experiments it was desired to subject a number 

 of plants to illuminating gas under conditions met with in the field 

 where leaking gas mains are involved. Potted woody plants, 

 including 36 individuals of 11 species, were used. Illuminating 

 gas was allowed to pass slowly into the soil around the roots. 

 Meanwhile symptoms of injury were noted. When the plant had 

 died, or become seriously injured, or after a certain time had elapsed, 

 the roots were washed clear of soil, and careful examinations made. 

 The rate of gas flow was often less than one-eighth liter per hour. 



Results and discussion 



The results will be presented in the order in which the methods 

 were described. 



A. EFFECT OF ILLUMINATING GAS ON SEEDS PLANTED IN SOIL 

 PREVIOUSLY TREATED WITH GAS AND THEN AERATED 



In all cases, at the time of the planting of the seeds, the treated 

 soil gave an exceedingly strong odor of illuminating gas. Of the 

 41 species planted, 5 failed to germinate, but the failure was in 

 both the controlled and the treated soils. Throughout the 25-60 

 day period, the aerial portions of the seedlings were watched for 

 signs of injury. However, it was found that the plants in all the 

 treated soils gave no superficial evidence of injury. All seemed 

 perfectly normal. At the end of the period the plants were taken 

 up, their roots, washed free of soil, and examinations made. Only 

 two species gave any evidence of injury; these were cotton and 

 lupine. In them the root systems were perhaps somewhat less 

 developed in the treated soils, and in the cotton there appeared to 



