1908] CROCKER AND KNIGHT— CARNATIONS 261 



reserve food had been exhausted. In another experiment he found 

 that soil impregnated with gas was very poisonous to plants, for 

 seeds put to germinate in it started, but their roots soon died. A 

 Dracaena planted in such soil died in ten days. Far less injury was 

 shown when a given quantity of gas was in contact with the portions 

 of the plant above the ground than when the same quantity came in 

 contact with the roots by being passed into the soil. The roots, he 

 concludes, are most sensitive to gas injury. He found potted plants 

 of Fuchsia and Salvia only moderately sensitive to illuminating gas 

 that was allowed to bubble through the soil. 



Lackner (7) states that camelias, azalias, cacti, and ivy are much 

 injured if kept in rooms where illuminating gas is burned; while 

 palms, dracaenas (Acuba japonica), and many other plants escape 

 uninjured. He asserts that it remains to be determined whether 

 it is escaping portions of unburned gas or products of incomplete 

 combustion that produce the injury. 



C. Wehmer (8) calls attention to a severe case of gas poisoning 

 in Hanover. Thirteen elm trees along a street showed injuries vary- 

 ing with the distance they stood from a leak in a gas pipe. In late 

 winter a number of them showed brown discoloration of the inner 

 bark, and a falling-off of bark in large patches extending up the 

 trunk six feet from the ground. No blue discoloration of the roots 

 appeared as was reported by Kny and other observers. The author 

 asserts that the area of the injury was especially great because of the 

 hard-packed street above the leak. 



Molisch (9) found that illuminating gas is more injurious to the 

 roots of plants than chlorin or carbonic acid. Growth in length is 

 retarded by 0.005 P er cent, of illuminating gas. If uninjured and 

 decapitated roots of corn are grown in illuminating gas, the former 

 are remarkably bent and retarded in their growth in length, while 

 the latter grow almost straight and are comparatively vigorous. 

 Under the influence of the gas the growth in thickness of the roots is 

 increased, the greatest thickening occurring where the bending 

 is sharpest. When a 10-20 per cent, mixture of illuminating gas 

 exerts a stimulus from one side, the roots respond negatively. 



Neljubow (10) notes some very interesting effects of illuminating 

 gas upon the etiolated seedlings of peas and other legumes. Wiesner 



