

1908] CROCKER AND KNIGHT— CARNATIONS 263 



entiation of the primary tissue, and in hindering the formation of 

 chlorophyll. Gametophytes of certain mosses were found to be 

 very resistant, suffering very little injury in high concentrations of 

 these gases for three months. A more delicate moss, presumably 

 Mnium undulatum, however, showed deleterious effects earlier. In 

 Elodea and Nitella older cells were most injured, and the injury was 

 shown by plasmolysis of the cells. A considerable part of their 

 experimentation with illuminating gas serves to confirm the results 

 obtained by Molisch, Neljubow, Bohm, and others. The con- 

 clusion that "illuminating gas affords, in addition to the action of 

 carbon monoxid, the results of the action of other substances dele- 

 terious to plants" seems to indicate that the work of Neljubow and 

 others was entirely overlooked. 



Stone (13) calls attention to the fact that very small leaks (2-3™- ft 

 per day), of gas may cause local injury to trees. Among manifesta- 

 lions of gas-killing in trees, he notes the early appearance of an 

 abundant growth of fungi in contrast to the relatively late appearance 

 on other dead trees. In speaking of the distance gas may travel he 

 says: "In gravelly soils we have known gas to travel 2000 feet 

 without difficulty, when the ground is frozen, and escape into the 

 cellar of a house; whereas in heavier soils gas is more likely to be 

 restricted to smaller areas." 



Richter (14) and other investigators have pointed out a number 

 of effects of impurities of laboratory air upon the responses of seed- 

 lings. Richter believes that in a number of cases the negative 

 geotropism of hypocotyls is greatly weakened by these impurities. 

 He points out that a one-sided illumination will produce far more 

 nearly a horizontal position with than without these impurities. 

 He likewise asserts that in many species the degree of horizontality 

 from one-sided illumination indicates the degree of impurity of the 

 air. He found great variation, however, in sensitiveness in different 

 species even of the same genus. 



2. Scope, method, and preparation of material 



It is quite commonly asserted that plants do poorly in houses 

 lighted with gas and especially is the flowering interfered with. 

 Various inquiries have come to us from carnation growers as to the 



