Physiologie. 295 



mining the changes brought about in plant tissues by ethylene. 



Ethylene was found to be very effective in producing changes 

 in the general processes of plant metabolism. 



Chemical analyses showed that ethylene caused the simple 

 soluble substances to increase at the expense of the higher soluble 

 and insoluble forms. 



a. The hot alcohol-ether soluble substances (sugars, amino acids, 

 amids, Polypeptides, lipoids etc.) increased by 8—9 per cent, while 

 the insoluble substances (proteins, starch, cellulose, lignocelluloses, 

 etc.) were correspondingly diminished. The water content of the 

 ethylene treated and control tissues was the same. 



b. The lower soluble sugars (by direct reduction) were about 11 

 per cent more and the higher soluble sugars (by reduction after 

 hydrolysis) about 3 per cent less. The reducing power of the alco- 

 hol-ether insoluble residue, after hydrolysis, was decidedly less for 

 the ethylene treated tissue; also, the cellulose content was dimini- 

 shed by about 3 per cent. 



c. Amino acid plus amids were more, and the Polypeptides 

 apparently less in the ethylene treated tissue. The protein content 

 also was about 3 per cent less. 



d. Fats were much less abundant in the treated tissue, The 

 free fatty acid value was unchanged. 



The acidity of the ethylene treated tissue was not found to be 

 changed. 



Ethylene caused an increase of osmotic pressure, as measured 

 both by the freezing point and plasmolytic methods. 



The permeability was not sharply aflfected by ethylene, although 

 it was somewhat increased. 



Ethylene affected respiration, retarding both the COg production 

 and the O2 absorption, but the respiratory ratio remained practi- 

 cally the same. An exception to the preceding Statement was found 

 in the case of the shortest exposure period (3 hours), in which there 

 occurred, apparently, an excessive production of CO2, thereby increa- 

 sing the ratio. Jongmans. 



Hapvey, E. M. and R. C. Rose. The effects of illuminating 

 gas on root Systems. (The Bot. Gazette. LX. p. 27—44. 9 Fig. 

 1915.) • 



That illuminating gas has a very injurious effect upon trees and 

 shrubs is well-known. The present investigation is undertaken with 

 two Problems in mind: 1) that of determining some of the effects of 

 illuminating gas on root Systems and 2) whether the chief causes 

 of injury are those constituents of illuminating gas which are rea- 

 dily absorbed by the water film of the soil particles, or those which 

 remain mainly in the soil interstices (not being so readily soluble). 

 The results of the investigation are following: 



When illuminating gas is passed through soil, the odor-giving 

 constituents of the gas are readily absorbed by the soil particles 

 and strongly held. These odorous substances are very slightly, if 

 at all, toxic to roots of plants growing in a soil containing them. 



The constituents of illuminating gas which remain in a gaseous 

 State in the soil interstices are the chief cause of injury to root 

 Systems. Among these constituents, ethylene is probably the most 

 harmful, except in extremely high concentrations of illuminating 

 gas, where the toxicity of other substances, together with other 

 factors, would be expecled to play a part. 



