1917] DOUBT— ILLUMINATING GAS 211 



opened and were of normal size. The one treated with gas showed 

 slight discoloration on the spathe. Four per cent of illumina- 

 ting gas, then, slightly injures the inflorescence of the calla lily. 

 Further results on the calla lily are given later. 



2. Exposure of entire potted plants was made in two wardian 

 cases (each of about 1000 liters capacity); one case was used for 

 exposure to gas and the other case was used for the control plants. 

 The plants were placed in the cases by the removal of a pane of 

 glass which was later sealed into place with the vaseline-clay 

 mixture used by Crocker and Knight. The plants were kept 



under moisture conditions as nearly optimum as possible. During 

 the winter season the temperature varied between 15 and 20 C. 

 with day and night. The experiments were carried on from Jan- 

 uary to July. In April the temperature became so high in the cases 

 as to injure the plants. The cases were then given a coat of white- 

 wash. As the temperature again rose, the cases were moved out- 

 side and partly shaded. Plants were treated for 2 days, then the 

 cases were opened, the plants removed, and the cases aired by 

 means of an electric fan. After watering, the plants were returned 

 to the case and following renewal of gas were left 2 days more. 

 They were then removed and the immediate and the after effect 

 of the gas noted. Since the control plants were in no case injured, 

 it is clear that the response of the other plants was due to the gas. 



Types of responses 



1. Leaf fall. — In certain concentrations of ethylene or of illumi- 

 nating gas, Mimosa, Lycopersicum, Salvia, Datura, Coleus, and 



Hibiscus 



The 



formed. The older the 



less gas was required to cause the older leaves to drop. The 

 youngest leaves were least affected. 



2. Rigor. 



Mimosa 



when subjected to large amounts of gas. Mimosa showed imper- 

 fect rigor, lost sensitiveness to touch, but was somewhat injured 

 by the gas. Coleus was completely anesthetized, with no ill after- 

 effects. Fitting (5) found that heat rigor or rigor from lack of 



oxv 



