194 BOTANICAL GAZETTE [September 



must be about i per cent. This illustrates how sensitive the sweet 

 pea seedling is to traces of ethylene. Moreover, it seems fairly 

 well demonstrated that for plants in general (but by no means all) 

 ethylene is relatively very toxic. 



The remarkable capacity of ethylene to induce swelling naturally 

 suggests the question, What is the effect of ethylene on plant 

 metabolism ? A certain amount of work has been published on the 

 effects of illuminating gas and "laboratory air," which should 

 furnish required data on the question, since in both those gaseous 

 mixtures ethylene has probably been an important factor. Never- 

 theless, with regard to the effect of ethylene as such, I have been 

 able to find no literature. This was largely the reason for under- 

 taking the investigation reported here, the work having as its sub- 

 ject the determination of the changes brought about in plant tissue 

 by ethylene. 



Historical 



Our knowledge of the changes in metabolism causing and accom- 

 panying swelling of plant organs has been gained largely from 

 investigation of the effects of anaesthetics, particularly ether and 

 chloroform. For a general historical resume of the literature of the 

 effects of anaesthetics on plants, the reader is referred to an excellent 

 paper by Hempel (ii). The following consideration of the litera- 

 ture deals only with the effects of anaesthetics on the chemical 

 composition and the respiratory processes. 



Johannsen (16, 1 7) found that certain concentrations of ether 

 and chloroform caused an increase of soluble sugars and a decompo- 

 sition of proteins in bulbs of Crocus and seeds of pea and barley. 

 But he also noted that very weak ether gave reversed effects, that 

 is to say, favored starch and protein synthesis. His explanation 

 for the increase in sugars and amino bodies was simply that anaes- 

 thetics interfered with the condensation, but not with the hydro- 

 lyzing processes. Zaleski (36), working with Lupinus, found that 

 protein synthesis was favored by ether and hindered by caffein. 

 Butkewitsch (3) and Bartel (2) both reported an increase of 

 tyrosin in Lupinus, as an effect of chloroform. Peianischnikow 

 (28) was able to demonstrate a considerable increase of asparagin in 

 Lupinus when the seedlings were grown in an atmosphere containing 



