858 LUMINOSITY AND ELECTRICITY OF PLANTS, 
2. Luminosity or Piants.—Very little is positively known 
respecting the development of light by plants. But it seems 
tolerably well ascertained, on the authority of Humboldt, Nees 
von Esenbeck, Unger, Drummond, and others, that the thallomes 
of some living Fungi are luminous in the dark. This luminosity 
has been noticed in several species of Agaricus and the so-called 
Rhizomorpha ; but Brefeld says that only the young hyphe are 
luminous in the latter. According to Prescott, the mycelium 
of the common Truffle is also luminous in the dark. 
The statement that certain Mosses, as Schistostega osmundacea 
and Mniwm punctatum are phosphorescent, appears to have been 
founded on imperfect observation. 
With regard to the development of light by the higher classes 
of plants, we have at present no very satisfactory observations 
to depend upon. It has been repeatedly stated, that many 
orange and red-coloured flowers, such as those of the Nastur- 
tium, Sunflower, Marigolds, Orange Lilies, Red Poppies, &c., 
give out, on the evening of a hot day in summer, peculiar 
flashes of light. This peculiar luminosity of orange and red 
flowers is now commonly regarded as an optical illusion, and the 
fact of such luminosity having been only noticed in lowers with 
such bright and gaudy tints, appears strongly to favour such a 
conclusion. 
The rhizomes of certain Indian grasses have been reported 
to be luminous in the dark during the rainy season; and 
Mornay and Martius have observed, that the milky juices of 
some plants were luminous when exuding from wounds made 
in them. Martius also states, that the milky juice of Hwphorbia 
phosphorea is luminous after removal from the plant, when it is 
heated. 
3. Exectrictty oF PLtants.— Disturbances of electrical equi- 
librium are undoubtedly connected with the various chemical 
and mechanical changes which take place in plants. By the 
medium of a galvanometer, Ranke, Velten, Burdon Sanderson, 
and others, have demonstrated that there exists in plants an 
electric current from the transverse to the longitudinal section 
of a vegetable fibre, similar, but in the contrary direction tu 
that shown by Du Bois Reymond to exist in the muscles, &c., of 
animals. It is also found that the internal tissue of land plants 
is always electro-negative to the cuticularised surface. 
The Effect of the Electric Light on the Growth of Plants and 
Production of Chlorophyll.Some experiments made by the late 
Sir Wm. Siemens seem to prove that the electric light aids the 
growth of plants, produces chlorophyll, increases the brilliancy 
of flowers, and promotes the ripening of fruits. By sowing seeds 
of rapidly growing plants and exposing them to the same con- 
ditions with the exception of light, he found that those grown 
in the dark were etiolated and soon withered ; those exposed to 
daylight with a fair share of sunlight were vigorous, and of a 
