VOLUME LV NUMBER 5 
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BOTANICAL (GAZETTE 
MAY 1913 : 
TOXICITY OF SMOKE 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 171 
LEE I. Kn1icGHt anp WM. CROCKER 
I. Introduction 
(WITH FOUR FIGURES) 
Extensive unpublished experiments have been conducted in 
this laboratory to determine the reliability of the etiolated epicoty] 
of the sweet pea as a test for the presence of traces of heavy hydro- 
carbons in the atmosphere. As an outgrowth of this work, we have 
had occasion to study the response of this organ to smoke pro- 
duced by the burning of various carbon-bearing substances, with 
the idea of discovering the constituent or constituents that pro- 
duce the response. 
The complete statement of the response of this seedling to gas- 
€ous impurities will involve two additional papers, one under the 
title “Is methane toxic?” and the other “The sweet pea epicotyl 
as a delicate test for heavy hydrocarbons.’’ Both of these papers 
will be published shortly. 
NELJuBow (25) has shown that the etiolated epicoty] of the pea 
seedling has an abnormal growth in “laboratory” or “impure” air. 
We may speak of the abnormality as a triple response: change of 
hegative geotropism to diageotropism, increased growth in thickness, 
and reduced rate of growth in length. We tested about 20 varieties 
each of garden peas and sweet peas, and found the sweet peas in 
337 
