334 LUMINOSITY IN PLANTS. [Sess., LXXxU. 
and mineral kingdoms, whether we take into consideration 
the colour of the light produced or the substance which 
shines, yellow and orange tints seem to predominate, and 
appear in some way connected with the phenomenon. Pro- 
fessor Haggern, the Swedish naturalist, studied the question 
of luminosity in flowering plants very carefully. He 
observed the phenomenon more or less marked in the 
common marigold, garden nasturtium, the orange lily, and 
the French and African marigold. Thinking that the 
phenomena might be due to phosphorescent insects, he 
examined the flowers with the microscope, but no such 
organisms were found. The rapidity of the flash, however, 
led him to believe that the phenomenon was due to electricity, 
the pollen, when freed from the anthers, being electrified and 
then alighting on the petals, from which the light was 
emitted. 
The Swedish botanist, M. Fries, also observed the pheno- 
menon of luminosity in the poppy. Thinking his eyes 
deceived him, he called others, and without an exception 
all remarked the phenomenon. One can scarcely believe that 
the case observed and others similar were optical illusions, 
as Pfeffer suggests they might have been; but that these 
phenomena are in some way connected with the condition of 
the atmosphere and with electricity is undoubted, since all 
the phenomena observed took place on warm. sultry evenings. 
According to Mornay and Martius, the latex of certain 
Euphorbias is phosphorescent. Pfeffer suggests that this 
is due to oxidatory photo-chemical changes on exposure 
to the air, or perhaps that the latex is infected with 
luminous bacteria. Evidently the phenomenon has not 
been thoroughly worked out, but research in this direction 
would be interesting. 
Another interesting case of luminosity in higher plants is 
that of the potato. It is said that in a state of decom- 
position it emits a bright light. The cause is most probably 
identical with that of luminous decaying wood, the luminosity 
of which is due to fungi. The fact of the luminosity of 
decomposing potatoes was remarked by an officer on 
guard at Strasburg, who thought the barracks were on fire 
in consequence of the light emitted from a cellar full of 
potatoes. 
