88 



The Plant World. 



hard-packed or frozen crust over the top. This paper shows 

 the extreme sensitiveness of the carnation to this substance. 

 From these facts it is evident that carnation growers whose 

 greenhouses are in the region of gas pipes must take great pre- 

 cautions against losses from this source. It would be inter- 

 esting to know whether solid cement walls set into the ground 

 for some depth on the side next the pipes would furnish sufficient 

 protection against leaks of this kind. It is clear that, if (as our 

 results would seem to indicate) the group of illuminants, or, 

 more accurately, if one constituent of this group (ethylene) 

 determines the toxicity of illuminating gas, coal gas is consider- 

 ably less toxic than water gas, while oil gas is more toxic than 

 either of the others; also the toxicity reported by the German 

 investigators who used coal gas is less than that shown by the 

 gas of the great American cities. 



While it seems probable that the limit of toxicity of illumi- 

 nating gas on the flower of the carnation is determined by the 

 ethylene it contains, it does not follow that such is the case 

 with all parts of the plant or even with the flowers of all plants. 

 It would be interesting to know the effects and toxic limits of 

 illuminating gas and its constituents upon various double as 

 well as single flowers. Similar data for the foliage of various 

 plants such as Coleus, which is supposed to be especially sensi- 

 tive to illuminating gas, would likewise be of great interest. 



During the winter months when the windows are closed we 

 have always been unable to cause plants to flower in our green- 

 house over the botany building. Thinking escaping illuminating 

 gas might be the cause, chemical tests were made for it, but never 

 showed its presence. In the face of the results given above, 

 chemical tests are of course entirely worthless. Such data as 

 are given here show the extreme care that must .be taken in 

 ordinary laboratories to avoid the vitiating effects of noxious 

 gases. We expect to carry out a series of experiments with all 

 the common gases of the laboratory, determining the nature and 

 degree of effects upon this very sensitive organ. Such a study 

 ought to show the gases to be feared most in connection with 

 a study of plant responses. 



Hull Botanical Laboratory y University of Chicago. 



