152 MISSOURI BOTANICAL GARDEN BULLETIN 
fungi have retained this power for one and one-half years, 
while cultures of bacteria emitted light for two years, the 
only limiting factor being that of nutrition. The phosphor- 
escence of wood is almost invariably due to a filamentous 
fungus, or the vegetative stage of a toadstool, which is causing 
its decay, while the phenomenon in dead tissues of animals 
may be attributed to phosphorescent bacteria, such as Bac- 
terwm phosphorescens, Microspira luminosa, ete. A rough 
estimate regarding the amount of light emitted by bacteria 
shows that it would require a colony 2,000 meters square 
to produce one candle power of light. ‘Bacterial lamps,” 
made by coating the interior of large flasks with nutrient 
media and inoculating them with phosphorescent bacteria, 
produce enough light to make reading of large type possible. 
Photographic plates are sensitive to the light emitted, a ten 
to fifteen-hour exposure, however, being necessary to satis- 
factorily photograph objects illuminated by “bacterial 
amps.” In but one instance was the light produced by a 
culture of these organisms strong enough to be resolved into 
‘spectral colors—green, blue, and violet. In all other cases 
no colors appeared, though a faint luminescence appeared in 
the yellow, blue, and green portion of the spectrum. 
Self-illumination of this nature is associated with meta- 
bolic activity and must be accounted for on_ biological 
grounds. It is the result of oxidative processes which, how- 
ever, are not of a respiratory nature, since an increase of 
the intensity of illumination does not necessarily result in 
an increase of carbon dioxide production. It should, there- 
fore, be looked upon as an indication of complex chemical 
oxidative changes in the living matter of the cells, rather 
than of simpler oxidation, as in respiration, which results 
in energy release and the immediate liberation of carbon 
dioxide. 
It is of interest to note that no other form of energy, as 
for example, heat, accompanies light radiation; at least the 
sensitive radiometers used were unable to measure any heat. 
That plants are capable of producing an appreciable amount 
of heat is, however, well known. The arums, of which there 
are a considerable number in the aroid house, present some 
of the most notable examples of this power. Arum italicum, 
at the time of the opening of the spathe, recorded a tem- 
perature of 44°C. immediately within the spathe, while the 
temperature of the surrounding air was 15°C. While this 
is probably the maximum amount of heat produced by a 
plant, it is believed that many, if not all, flowers show a 
rise of temperature at the time of opening. 
