Mar. 1908. | LUMINOSITY IN PLANTS. 335 
Though the facts are interesting, not really much import- 
ance can be attached to the so-called luminosity of higher 
plants. It is among the lower plants, especially among the 
fungi and bacteria, that the phenomenon is more striking. 
A little moss, Schistoslega osmundacea, the protonema of 
which gives forth a faint emerald-green light, was supposed 
formerly to be luminous, but it has since been clearly shown 
that the phenomenon is one of reflected light. Leaving this 
plant, therefore, out of the question, also the wonderful 
iridescence of many sea-weeds, Professor Molisch says that 
phosphorescence in the plant world may be said to be 
confined to the fungi—that is to say, bacteria and mycelial 
fungi. 
Let us first consider fungi. Many agarics exhibit the 
phenomenon of luminosity. Agaricus melleus is one which 
is most commonly met with, perhaps, but there are other 
species, ¢.g. A. olearivs, growing at the foot of olive trees in 
Italy, A. noctilucens, Gardneri, etc. M. Delille and Fabre and 
Gardner have studied these agarics in some detail. Another 
fungus which is luminous, common in dark, damp mines, 
is Rhizomorpha subterranea. The effect of the light in 
the mines is said to be very pretty, but nowhere perhaps 
is it more beautiful than in the mines of Hesse in N. 
Germany. 
The phosphorescence of decaying wood has been shown to 
be due to the presence of fungi. Perhaps the latest work in 
this direction has been done by Professor Molisch of Prague. 
He also states that he found decaying leaves quite luminous, 
e.g. those of oak and beech. The luminosity is not always 
due to the same cause, There is a byssoid fungus which is 
said to be commonly found on old willows—Thelephora 
cerulea, so called from the blue colour of the mature plant. 
Xylaria hypoxylon is also responsible for the phenomenon. 
Bockman has shown that dampness is necessary for the 
luminosity of decayed wood, and made many interesting 
experiments in connection with the subject. 
To pass on to the luminosity of bacteria: considerable 
work has been done in this connection, especially in late 
years, by Molisch and by Beyerinck. The former has in- 
vestigated the cause of phosphorescence in fish and meat, and 
has shown that the phenomenon (which is of sO common 
