1915] 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 Kosarorr (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 
2 : Fic. 6.—Diagrams of transverse sections 
Foots were killed quickly by of Aitanthus roots; A, control; B, treated 
using high concentrations of with illuminating gas; s, stele; c, cortex; 
e, epidermis and tissue lying outside of 
hellogen; x, new tissue developed by the 
phellogen; X6. 
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 to 
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. 
