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 Euphorbia 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 light thus emitted from a cellar full of 

 potatoes. This phosphorescence resembles that 

 of stale fish, but it is perhaps attributable to the 

 same cause as that of decayed wood, treated of in 

 the next chapter. 



