VEGETABLE PHOSPHORESCENCE. 805 



of inexorable law are as fully met in the pale glimmer of luminous 

 plants, the flash of the fire-fly, or the radiance of the glow-worm, as in 

 the light evolved by the heavenly bodies. 



The discovery of the luminosity of plants has been attributed to 

 the daughter of Linnaeus. In the year 1762, during the months of June 

 and July, she observed radiations of light from a cluster of garden 

 nasturtiums {Tropcelum mq/us), which occurred in the morning or 

 evening twilight. The same effect has been observed in other flower- 

 ing plants, but principally in those bearing orange-colored bloom, as 

 the corolla of the sunflower, the French marigold, and in the yellow lily. 

 Some species of African marigolds also have manifested this pi'oper- 

 ty. Professor Haggern observed the luminous radiations to be most 

 brilliant in the marigold, next in the nasturtium, and, third, in the yel- 

 low lily. A careful microscopic examination convinced him that the 

 light did not depend upon the presence of any animal organisms. The 

 rapidity of the flash indicated electrical action, and upon analysis he 

 found that the light proceeded from the petals, the anthers being at 

 an appreciable distance. He supposed that in the process of fecunda- 

 tion the elasticity of the anthers scattered the pollen on the petals and 

 produced electrical disturbance by the imjDingement of these different 

 substances. In bog or marsh land plants, of the genus I*andanus, the 

 rupture of the spathe or shield of the flowers is sometimes accompanied 

 by a loud, cracking noise and a spark of light. In 1857 M. Fries per- 

 ceived light emitted by a group of poppies {Papaver orietitale) in the 

 botanical garden at Upsal, to which he called the attention of numer- 

 ous witnesses. 



The phosphorescence discovered by the daughter of Linnaeus bore 

 the character of an electrical spark which shot out from the corolla 

 and was discernible at the same hour upon warm evenings when the 

 air was surcharged with electricity. The radiance noticed by M. 

 Fries also indicated a periodicity of movement, occurring always when 

 the air was electrical, between ten and eleven o'clock at night. Not 

 only the blossoms but the leaves of many of the flowering plants have 

 been observed to emit a phosphoric light under favorable conditions 

 of the air — even the milky juice of several vegetables becomes lumin- 

 ous in the dark ; this was particularly noticed by M. Martins in a spe- 

 cies of the phosphorescent spurge {Euphorhici). 



The giving out of heat in the blossoming of plants was discovered 

 by Lamarck more than a century ago in the Eui'opean arum, which in 

 opening " grows hot as if about to burn." It was afterward observed 

 by De Saussure, and by the later appliance of the thermo-multiplico 

 the heat generated in any cluster of blossoms is made appreciable. 

 The development of this force is most remarkable in tropical plants, 

 where a large number of flowers are crowded together under a cover- 

 ing hood of spathe. The temperature increases periodically, growing 

 greater in the afternoon and appearing like a " paroxysm of fever " 



