50 EXPERIMENT STATION. [Jan. 



ping off, peeling of the bark, presence of certain fnngi, etc., but 

 they are of no value in themselves, as these symptoms may 

 accompany other causes of death. 



The Effect of Illuminating Gas on Foliage. 



Gas from soil leakage seldom escapes into the atmosphere 

 sufficiently to cause direct injury to foliage, although trees are 

 sometimes injured near gas-manufacturing plants, where there 

 is usually a strong odor of gas. Atmospheric gases of all kinds 

 are quickly dispersed, especially when there is any circulation 

 of air ; yet under certain conditions they cause injury to plants, 

 as is well known. The leakage of illuminating gas from soil 

 pipes is seldom sufficient in quantity or prolonged enough for it 

 to injure the foliage of trees and shrubs. 



The trees in large cities often suffer greatly from atmospheric 

 gases, of which the most injurious are those arising from coal 

 combustion. The escape of illuminating gas into sewers and 

 conduits is not uncommon. If an untrapped greenhouse drain- 

 age system connects with a sewer containing gas, the gas is likely 

 to find its way into the greenhouse and injure the plants, and 

 we have known of large greenhouses losing many plants in this 

 way, the gas escaping into the greenhouse for long periods in 

 such minute quantities as to be scarcely perceptible to the sense 

 of smell. Last winter, when the upheaval of the ground from 

 frost did great damage to gas and water pipes, the gas from a 

 leak near our greenhouse found its way to a drain tile leading 

 to the house some distance from the source of leakage, defoliat- 

 ing a large number of our plants in a few hours. A rose plant 

 which was in perfect condition the night before was found the 

 next morning with most of its leaves turned yellow, and 50 or 

 more per cent, of them had fallen. The plants most severely 

 affected were roses, geraniums and abutilon, but ivy. Euca- 

 lyptus, India rubber plants, willow, Kenilworth ivy, papyrus, 

 tobacco, tomato and Sedum were also injured. The ferns, 

 mosses and liverworts, which were nearest the gas inlet, were 

 scarcely touched. After being defoliated, the geraniums and 

 abutilon produced numerous small leaves, and the leaves on the 

 variegated abutilon came in entirely green. 



