HARVEY &■ ROSE— ILLUMINATING GAS 



39 



inert gas (that is, nitrogen or hydrogen) be passed through the 

 soil in this manner. Accordingly, illuminating gas could do great 

 damage to vegetation independent of any direct toxic property. 

 This view is advanced by Kosaroff (9), who found that wilting 

 took place if a stream of carbon dioxide or of hydrogen was passed 

 through soil in which roots were growing. In all experiments where 

 illuminating gas was passed into the soil rapidly enough to cause 

 the death of the plant, the symptoms manifest in the aerial parts 

 were of a type which would indicate that the injury might be due 

 simply to the cutting off of the water supply as a result of injury 

 to the root system, and not, necessarily, due to a conduction 

 of toxic substances to them. 

 With high evaporating con- 

 ditions, the symptoms of gas 

 injury (that is, wilting, 

 yellowing, and falling of 

 leaves in the aerial portions) 

 always became manifest very 

 much sooner than under con- 

 ditions favoring a low water 

 loss. It was found that when 

 roots were killed quickly by 

 using high concentrations of 

 gas, few if any symptoms 

 other than odors appeared 

 which might enable one to 

 diagnose the death as specifically gas poisoning. With regard to 

 the injury to parts above soil, Stone (16) believes that "poisonous 

 principles" are absorbed by the roots and conducted upward U> 

 the leaves, hence the yellowing and wilting would result as a direct 

 poisoning of them. 



When illuminating gas was so regulated that it passed very 

 slowly to the roots (sometimes as little as 40 cc. per day), a stimula- 

 tion of the roots often took place, resulting in the development of 

 new tissue resembling those reported from the quantitative experi- 

 ments made with young tree seedlings. Stems were likewise 

 affected when covered by soil or when slightly above the surface. 



Fig. 6. — Diagrams of transverse sections 

 of AUantkus roots; A, control; B, treated 

 with illuminating gas; s, stele; c, cortex; 

 c, epidermis and tissue lying outside of 

 phellogen; X, new tissue developed by the 

 phellogen; X6. 



