232 



PHYSIOLOGY OF GROWTH AND CONFIGURATION 



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

 grow etect 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. III). Many different kinds of gases and vapors are thus injurious to the 

 growth of plants.' 



Fig. III.' — Pea seedlings grown in darkness; I and /// in laboratory air containing illumin- 

 ating gas, // in the same air with the poison gas removed. (After Neliubm.) 



A B 



Fig. 112. — Effect of ether upon the flowering of lilac. All shoots excepting the fiftb 

 from the left (as seen in .4) 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 Beschftdigung der Vegetation dutch Rauch; Handbuch mi 

 Erkennung und Beurteilung von Rauchschaden. 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. ipog. Idem, Toxicity of smoke. Hot. gaz. 55: 337-371. 1913. Crocker, W., Knight, 

 1. 1., and Rose, R. C, A new method of detecting traces of illuminating gas. Science, n.s. 31 : 636. IQIO-I 



