LETHAL GASES 



173 



as a point for diagnosing gas injury, if not on the trees killed, at least in 

 adjoining shrubs and trees that received a lower dosage of the gas. 



Hitchcock, Crocker, and Zimmerman '^ later reviewed the literature and 

 carried out many experiments on injury to plants by illuminating gas 

 seeping through the soil. 



Exposure of Roots in Soil to Flowing Gases 



The tomato plant proved to be very sensitive to illuminating gas flowing 

 through the soil in which it grew, and was much used in this investigation. 

 Fig. 64B shows that 2 cubic feet of Yonkers illuminating gas flowing 

 through a pot bearing a small tomato plant leads to the final death of all 

 the roots and the lower part of the stem, so that the plant later collapsed. 

 Even 1 cubic foot of gas killed the root system. Table 20 shows the effect 

 of flo^ving several different gases through the soil of pots bearing six differ- 

 ent kinds of plants. The most toxic of these gases is unscrubbed Yonkers 

 illuminating gas. Even 1 cubic foot of this killed all the roots, and 4 cubic 

 feet killed all the underground parts of the tomato plant, which collapsed. 

 The injury decreased in the following order for the other plants: willow, 

 maple, cherry, silver bell, and privet. Scrubbing the gas through water 

 before passing it through the pots reduced the toxicity measurably for all 



Table 20. Effect on Potted Plants of Passing Illuminating Gas and Certain of Its 

 Unsaturated Hydrocarbon Constituents Through the Soil for a Period of 30 Minutes 



* signifies no noticeable injury, + slight discoloration, + -f noticeable discoloration 

 and death of part or all of many roots, -f- + + aU roots badly discolored and most slender 

 roots killed. 



t All underground parts killed. 



