INFLUENCE OF ILLUMINATING GAS ON BACTERIA AND FUNGI 29 
at this degree of concentration reaction was obtained. In the case of 
the 25 cryptogams reported in the present paper, however, there was 
uniformly no visible reaction at 5 percent. So far as present records 
go, therefore, the phanerogams which are most tolerant to illuminating 
gas are not more tolerant, indeed are apparently less so, than the most 
sensitive bacteria and fungi. In other words, the least sensitive 
phanerogams are more sensitive than the most sensitive bacteria 
and fungi. It was also a matter of surprise, in view of the extreme 
toxicity of ethylene to phanerogams, to find that it is relatively 
innocuous to the cryptogamic species studied. In this case carbon 
monoxide was found to be considerably more toxic than any other 
organic constituent of illuminating gas. The fact that ethylene is 
more toxic to one group of plants and carbon monoxide to the other 
is further evidence of a great difference in the sensitivity of the two 
groups. 
Incidentally it may be remarked that so far as the results from the 
species studied in this investigation can be projected to cover all 
species, they indicate that there is only a small chance that the gas 
which would escape from the gas fixtures in a room would be enough 
to invalidate results obtained from cultures in that room. It should 
be remembered, however, that even phanerogams vary considerably 
in this regard, as has recently been shown by Miss Doubt (3) and 
others; also that at least some algae appear to be quite sensitive, as is 
reported by Woycicki (17, 18). It would not be at all surprising, 
therefore, and is perhaps to be expected, even, that some more sensi- 
tive bacteria and fungi will yet be found. The known existence of 
only a few such would render precautions necessary in bacteriological 
and mycological work which in the light of the results here reported 
seem unnecessary. 
CONCLUSIONS 
1. None of the species of cryptogams studied, including 13 bacteria 
and 12 fungi, shows any very marked sensitiveness to small amounts 
of illuminating gas or its components. 
2. In the higher concentrations (25 percent and above) of the gas 
and its components, however, most of the bacteria and fungi used are 
checked in growth or wholly stopped. In the latter case growth will 
usually take place after exposure to the air, although often from a 
comparatively few foci, as if many of the cells had been killed. Some- 
times the culture is entirely sterilized. 
