292 GENERAL PLANT PATHOLOGY 



work in Italy has been done by Brizi,in England by Crowther and Rus- 

 ton.i Recently in America J. F. Clevenger has published a bulletin 

 (No. 7), on "Smoke Investigation" for the Mellon Institute of Indus- 

 trial Research and School of Specific Industries, University of Pitts- 

 burgh, 1913, with plates showing the effect of the smoke on the struc- 

 ture of the woody specimens examined by him. 



Illuminating gas absorbed by the soil from nearby gas pipes is 

 injurious to trees and has frequently killed them outright, as instance 

 a group of street trees in Merchantville, N. J., a few years ago, wnich 

 were killed in this way, and for which the owner, Edwin C. Nevin, 

 received damages from the gas company for $1500, as a result of a 

 successful lawsuit. All the ordinary gases used for hghting and 

 heating are injurious and act much in the same way. Such are water 

 gas, coal gas, gasoline, acetylene and others. The first effects of gas 

 poisoning, may be seen in the foliage. The leaves turn yellow and in 

 some cases drop off, while the leaves of other trees fall while still green. 

 The water containing the gas in solution passes into the stem and the 

 wood and the cambial portion becomes abnormal. The underlying 

 tissues, cortex, bast and cambium die. Soon various species of fungi 

 gain access to the tree and cause its decay. With the CaroUna poplar 

 especially, the bark, cortex, etc., on the trunk towards the source of 

 absorption showed three or four vertical cracks, or lesions, one-half to 

 two and a half feet long. The bark on the sides of these cracks bulged 

 out considerably, and an investigation showed a thick layer of soft 

 parenchymatous tissue extending to the wood and derived from the 

 cambium zone. Later this tissue turned brown, disintegrated and 

 became slimy in appearance, the slime exuding from the cracks. 

 Illuminating gas dissolved in water in which willow cuttings were kept 

 stimulated the opening of the foliage buds several days earlier than plants 

 grown in water not charged with the gas. Stone^ found that the effect 

 of gas on lenticels was to increase their size, especially under water 

 charged with the gas. This appears to be a general response on the 

 part of the plant tissue to a demand for oxygen. 



That the trees, shrubs and flowering plants in our large cities and 



'Journal of Agricultural Science, 4: 25, 1911. 



2 Stone, G. E.: Effects of Illuminating Gas on Vegetation; 2Sth Annual Rep. 

 Mass. Agric. Exper. Stat., January, 1913; Shade Trees, Characteristics, Adapta- 

 tion, Diseases and Care. Bull. 170, Mass. Agric. Exper. Stat., Sept., 1916, p. 220. 



