274 BOTANICAL GAZETTE [October 



gas. The most delicate application of the blood te'st (see Hempel, 

 p. 225) will detect 1 part of carbon monoxid per 40,000. The iodine 

 pentoxid test (see Hempel, p. 226) is of equal delicacy. If carbon 

 monoxid forms 25 per cent, of illuminating gas, these tests will detect 

 1 part of illuminating gas in 10,000. Upon three days' exposure 1 

 part of illuminating gas in 40,000 kills the young buds and the petals 

 of the flowers just beginning to open; while 1 part in 80,000 causes 

 open flowers to close upon an exposure of twelve hours. 



The so-called "sleep" or closing of the carnation is a source of 

 considerable loss to growers and dealers, for flowers that once close 

 never again open. This "sleep" is especially likely to occur with cut 

 flowers brought into city markets. Some varieties are so disposed to 

 react in this way that their cultivation has almost entirely ceased. 

 We know several homes lighted with gas where cut carnations can be 

 kept only a few hours without "going to sleep." In one instance 

 the displacement of gas lights by electric lights entirely overcame 

 this difficulty. Our experiments show clearly that one cause of this 

 sleep is traces of illuminating gas (ethylene) in the surrounding atmos- 

 phere. 



Stone (13), Wehmer (8), and others have shown that illuminating 

 gas diffuses great distances through the soil, especially if there is a 

 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 precautions against losses 

 from this source. It would be interesting 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 seem to indicate) the group of illumi- 

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

 determines the toxicity of illuminating gas, coal gas is considerably 

 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 illuminating 

 gas on the flower of the carnation is determined by the ethylene it 



