178 



GROWTH OF PLANTS 



Figure 67. Effect on growth of tomato of leaching highly toxic gassed soil with water. 

 Left to right: control; soil from a 65-liter lot through which 7210 cubic feet of illuminating 

 gas had been flowed; a similar sample of gassed soil after leaching with an amount of 

 water equal to ten times its volume. Photographed three weeks after planting. 



Addition to the Soil of Other Compounds Present in Illuminating Gas 



Drip oils, i.e., oils condensed from illuminating gas at low temperatures, 

 caused the young tomato plant to collapse when 1 gram was mixed mth 

 450 grams of soil. The injury caused by these oils could not be distinguished 

 from injury caused by adding solutions of cyanides or passing unscrubbed 

 illuminating gas through the soil. The weight of drip oil that had to be 

 added to produce a given injury was more than 100 times the weight of 

 hydrocyanic acid or cyanides necessary to produce the same degree of 

 injury. It is not uncommon to find the soil near leaks in gas lines dis- 

 colored by drip oils. They persist in the soil for a long time and of course 

 ^\^ll injure roots growing in the soil bearing them. Drip oils were more 

 toxic than equal weights of toluene or xylene which, along with these, exist 

 in illuminating gas in small amounts. Phenol in high concentrations killed 

 the tomato, as did illuminating gas. It also caused a deep pink or reddish 

 coloration of roots, stems, and leaves of the tomato and of the roots of privet 

 and sunflower. Heavy dosages of illuminating gas produced similar color 

 changes. The color change induced by phenol is one of the symptoms that 

 should be looked for in diagnosing illuminating gas injury to trees and 

 shrubs. 



Diagnosis of Tree and Shrub Injury by Artificial Illuminating Gas 



As we have seen, it is easy to diagnose a case of illuminating gas injury 

 in a greenhouse. At the time the injury is occurring, reliable test plants can 



