CARBON MONOXIDE AND OTHER GASES 63 
Effect of nitrous oxide. — N,O was prepared from NH,NO,, and 
purified over ferrous sulphate, potassic hydrate and water. Seed- 
lings of mustard were arranged in the bell-jars in the same man- 
ner as in the CO experiments, except that a mercury seal was used. 
At the beginning of the experiment the hypocotyledonary stems 
of the seedlings were on the average 4 mm. long. After five days 
those of the control were 5 cm. and of the ones in 80 per cent. 
N,O, 2.6 cm., while the average of those in 40 per cent. N,O was 
about half-way between the two. The root-system also showed 
the effect of the gas, being both shorter and less branched in the 
seedlings exposed to the N,O. 
A trial experiment was also made with fungi to see if these 
plants could use the gas as a source of nitrogen. Three parallel 
Series were set up, one with a normal culture fluid containing a 
nitrate and two with the same culture fluid minus the nitrate. Of 
the last two, one was left in air, the other exposed to an atmo- 
sphere containing about 60 per cent. N,O, and normal oxygen. 
Up to this time neither of the series without nitrates have shown 
any development, while the control with the normal culture 
solution has produced a thick fruiting felt. The fungi used were 
Sterigmatocystis nigra, Penicillium glaucum and Rhizopus nigricans. 
It has, indeed, been reported somewhat indecisively that nitrous 
oxide can serve as a nitrogen source, but these negative experi- 
ments do not agree with such a conclusion. 
Another phase of the influence of the gases was to be found 
in their action upon the shoots and roots of woody or succulent 
perennials. If the basal portion of a shoot of such plants as Gos- 
Sypium or Haematoxylon were enclosed in a bell-jar with the stem 
extruding through a tubulure properly sealed around it, both illu- 
Minating gas and carbon monoxide acted as a very slow poison 
Which caused the leaves to become desiccated and to fall off after 
Periods varying from about four to twenty days, and the plants 
Were killed. 
_If entire plants of Haematoxylon, Mimosa, Metbomtia (Desmo- 
dium), Opuntia or Mesembryanthemum, were enclosed in the bell-jar 
Containing the gases, several important reactions might be noted. 
First it was to be seen that if the enclosing chambers were filled with 
a mixture of carbon monoxide or illuminating gas containing ove1 
