262 BOTANICAL GAZETTE [ocroBER 
had already reported a horizontal nutation of these seedlings, which 
he explained as autonomic. RrimMeEr later explained this horizontal 
growth as a response to unfavorable conditions, especially lack of 
moisture in the air. NELJUBOW found that while this response 
always occurred in the dark in the laboratory air, it did not occur in 
the dark in a greenhouse or in the outside air. After determining 
that temperature and moisture were not factors, he sought the expla- 
nation in impurities of the laboratory air. He found that laboratory 
air passed through KOH, Ba(OH),, CaCl,, red hot CuO, and finally 
through Ba(OH), gave vertical seedlings; while similar treatment 
with the CuO unheated gave seedlings with the horizontal placement. 
This proved that some impurities (probably some of the constituents . 
of illuminating gas) of the laboratory air, which were oxidized by 
glowing CuO, caused this peculiar horizontal placement. He later 
produced the effect with mixtures of illuminating gas, He likewise 
tested a number of the constituents of illuminating gas. Acetylene 
produced this nutation, but was difficult to work with, because, 0? 
the one hand, a slight increase in concentration killed, and on the 
other, it rapidly disappeared because of its high solubility in water. 
ne part of ethylene in 1,000,000 of air gave the response, while one 
part in 4000 killed the majority of the seedlings. He likewise mer 
tions the fact that various other constituents (benzene, sulfur dioxid, 
hydrogen sulfid, and carbon bisulfid) of illuminating gas are highly 
toxic. -He makes no attempt, however, to determine the toxic limits 
of the several constituents, or to learn whether one or several deter 
mine the toxic limit of illuminating gas. a 
SHONNARD (II) mentions several manifestations of the injury 
of illuminating gas to trees, and describes an experiment with a potted 
lemon tree exposed to a flow of 1.07% of gas per hour. After 
eight days he notes the exudation of sap in considerable quantity 
from trunk and branches, as well as the discoloration and falling-off 
of the leaves. 
RicHarDs and MacDovucaL (12) tested the effect of carbon 
monoxid and illuminating gas upon various seedlings. a 
monoxid, heretofore considered neutral, was shown to be Scat 
was not so effective as illuminating gas, however, in modifying : 
rate and amount of growth of root and shoot, in retarding the differ 
