PHANEROGAMIC PLANTS. 87 
light when the air is highly charged with electri- 
city. 
The latex or milky juice of some vegetables 
becomes phosphorescent when it is rubbed upon 
paper, or when it is heated a little. This is ex- 
tremely remarkable in Huphorbia phosphorea, a 
Brazilian species, which I believe has also been 
met with in Asia. If its stem be broken, and the 
milky juice which exudes be drawn over paper, 
characters are obtained which appear luminous in 
the dark, It is to M. Martins, of Montpellier, 
that we owe the discovery of the phosphoric pro- 
perty of this plant. 
An emission of light has also been observed in 
a plant closely allied to the Palm family, and 
which belongs to the genus Pandanus. The rup- 
ture of the spatha which envelopes the flowers of 
this genus of plants, is accompanied by a loud 
cracking noise, and a spark of light. 
The common potato in a state of decomposi- 
tion sometimes emits a most vivid light, sufficient 
to read by. This fact was remarked some time 
ago by an officer on guard at Strasburg, who 
thought the barracks were on fire, in consequence 
of the ight thus emitted from a cellar full of 
potatoes. This phosphorescence resembles that 
of stale fish, but it 1s perhaps attributable to the 
same cause as that of decayed wood, treated of in 
the next chapter. 
