1 9 1 S 1 



HARVEY &■ ROSE— ILLUMINATING GAS 



41 



experimental tree through a glass tube thrust 0.7 m. into the soil, 

 0.6 m. from the base of the tree. The rate of flow of gas was 1 . 5 

 liters per hour. The experiment began July 3, and the gas was 

 stopped flowing September 2. Except for two or three short periods. 

 amounting in all to less than three days, the flow of gas was 

 continuous during the two 

 months. Thus the soil 

 near the tree must have 

 received 1.5-2 cubic 

 meters of gas. 



The first symptoms of 

 injury were manifest July 

 14. Leaves of some of the 

 young shoots, growing on 

 the same side of the tree 

 from which the gas entered 

 the soil, showed signs of 

 wilting. Three days later 

 these leaves and others 

 had shriveled and died, 

 but remained attached to 

 the shoots. In some cases 

 only a portion of a leaf 

 was injured. A few leaves 

 of older branches also 

 wilted, but there was no 

 general effect evident 

 throughout the tree at that 

 time. In the middle of 

 September the apparently 

 unaffected leaves began to 



fall, and finally the tree was free from leaves much before those 

 of the controls. In October the tree looked as though it were 

 entirely dead, and when an examination was made, after it had 

 been removed from the soil, such was found to be the case. A 

 general dryness of the tissues was noted, but neither anatomical 

 changes nor gas odors were detected in them. 



Figs. 8, q. — Fig. 8, transverse sections through 

 cortex of Hibiscus at base of stem; X40; A , con- 

 trol; />', treated with illuminating gas; fig. g, 

 same for lilac; X35. 



