142 



HUTCHINSON'S POPULAR BOTANY 



place among luminous plants (fig. 177). To quote 

 from Erasmus Darwin : 



What time the eve her gauze pellucid spreads 

 O'er the dim flowers, and veils the misty meads, 

 Slow o'er the twilight sands or lealy walks, 

 With gloomy dignity Dictamna stalks ; 

 In sulphurous eddies round the weird dame 

 Plays the light gas, or kindles into flame. 



FIG. 178. LUMINOUS Moss I n plain prose, the plant secretes a fragrant essential 

 (Schistostega osmundacea). Q ^ ^ n g rea t abundance : and in warm weather this 

 The so-caiied luminosity is a false exudes anc i volatilizes, so that the air becomes 



appearance due to the reflection of .,.',. 



light from certain ceiis. impregnated with it. and is rendered not only very 



fragrant, but also highly inflammable ; insomuch 



that, if a naked flame be brought near the plant, the oily vapour takes 

 fire. This discovery, like that of the luminosity of Tropceolum, was made 

 by the gifted daughter of Linnaeus, and has been verified since by Dr. 

 Hahn, the result of whose investigations is given in the Journal of Botany 

 for 1863. His first experiments were unsuccessful, but on bringing a 

 lighted match to a nearly faded blossom, he saw " a reddish, crackling, 

 strongly shooting flame, which left a powerful aromatic smell, and did not 

 injure the peduncle." Since then he has repeated the experiment several 

 times, and a careful microscopic examination of the plant has shown that 

 the inflammable etheric oil is contained in numerous minute reddish brown 

 glands, located in the flower-stalks. 



Other instances of luminosity in Flowering Plants which, however, 

 must be more quickly passed over are afforded by 

 the latex or milk-sap of a species of Euphorbia (E. 

 phosphorea), which is said to shine with a phos- 

 phorescent light on warm nights in the ancient 

 forests of Brazil, and by the roots of certain plants, 

 as the fragrant Khus-khus (Andropogon) and other 

 grasses. A luminous rootstock referred to in the 

 Proceedings of the Royal Asiatic Society for April, 

 1845, is perhaps that of the Khus-khus grass. 

 After a wet cloth bad been applied to its surface 

 for an hour or two it gleamed in the dark "with all 

 the vividness of a glow-worm " ; and though the 

 lustre faded away as the specimen dried, it was 

 revived on the application of fresh moisture, nor 

 did it appear to lose its luminous property after 

 frequent applications. The sap of the Cipo, a South 

 American Vine, is said to be so highly luminous 

 Greatly magnified. that, when injured, it seems to bleed streams of 



FIG. 179. THREAD-LIKE 



GROWTH (PROTONEMA) OF 



LUMINOUS Moss. 



