260 BOTANICAL GAZETTE (October 



toward the periphery. The following spring the maple, elm, and 

 Euonymus bush showed no signs of life. The lindens produced 

 foliage, but the leaves were bleached and smaller than usual. Dried 

 cambium and a rich growth of fungi were further indications of 

 injury. 



Similar investigations were carried on by Spath and Meyer (4). 

 In one case during the summer a little less than i cu - m of gas diffused 

 daily through i'] .S" 1 - 111 of soil in a wooded plot. The roots of all the 

 trees were killed within a few days. During four winter months 

 the same amount of gas was allowed to escape into a wooded plat 

 of twice the above area. In this case Platanus, silver poplar, Ameri- 

 can walnut, and Ailanthus were killed; the maple and horse chestnut 

 were greatly injured; while the linden showed no injury. In another 

 experiment o.oi85 cu - m of gas was daily distributed equally among 

 seventeen trees. The experiment lasted from April 11 to June 27. 

 Before May 30 six of the more sensitive trees had died. By June 21 

 all the others, with the exception of the rough-fruited maple, had 

 slackened their growth. The leaves of the injured trees were a pale 

 green or yellow, and most of the younger roots were dead. According 

 to the statement of the gas inspectors, their methods were not capable 

 of detecting such light leaks as are shown in this experiment. These 

 investigators found that when the surface of the soil is compact, the 

 gas may travel long distances before reaching the surface. An 

 instance is cited of gas traveling from a leak on one side of a street 

 to a cellar on the opposite side, where it became evident by an unbear- 

 able smell. These investigators concluded that trees are far less 

 sensitive to gas leaks during the winter than during the growth period. 

 They also found much more rapid injury where the surface of the 

 soil was packed. The small quantity of gas necessary to kill and 

 the great distance that gas travels through the soil serve to empha- 

 size the danger to which trees are exposed. 



H. Eulenberg (5), besides summarizing the results given in 

 previous literature, adds the birch to the list of less sensitive trees. 



J. Bohm (6) grew slips of water willow in water through which 

 gas was passed. He found that they produced only short roots and 

 that these soon died, as did also the buds. The twigs themselves 

 remained alive for about three months, until, as he believes, the 



