2Ö2 



PHYSIOLOGY OF GROWTH AND CONFIGURATION 



ethylene and acetylene, which are present in illuminating gas. The shoots 

 grow erect in an atmosphere without illuminating gas, but when even very min- 

 ute traces of this gas are present they bend and assume a horizontal position 

 Fig. in). Many different kinds of gases and vapors are thus injurious to the 

 growth of plants.' 



Fig. hi. — Pea seedlings grown in darkness; 1 and III in laboratory air containing illumin- 

 ating gas, II in the same air with the poison gas removed. {After Neliubov.) 



А В 



Fig. ii2. — Effect of ether upon the flowering of lilac. All shoots excepting the fifth 

 from the left (as seen in A) were treated. The untreated shoot is seen unaltered in B, where 

 the others are all in full leaf and flower. 



1 Haselhoff, Emil, and Lindau, G., Die Beschädigung der Vegetation durch Rauch; Handbuch zur 

 Erkennung und Beurteilung von Rauchschäden. Leipsig, 1903. [In this connection, see: Crocker. W., 

 and Knight, L. I., Effect of illuminating gas and its constituents on flowering carnations. Plant world 

 12: 83-88. 1909. Idem, Toxicity of smoke. Bot. gaz. 55 = 337-371- 1913- Crocker, W., Knight, 

 L. I., and Rose, R. C, A new method of detecting traces of illuminating gas. Science, n.s. 31 : 636. 1910.] 



