§24 Transactions of the American Institute. 



class having spontaneous motions without any apparent cause. 

 Until lately, only one plant was known to be thus aflected — the 

 Hedysarum gyrans. Mr. H. Lecoq reports to the French Academy 

 of Sciences a similar action in the Colocasia esculenta. On visiting 

 his hot-house in Januaiy last, he perceived a motion in one of the 

 leaves of this plant. At first he attributed it to a draft, but on 

 examination, remarked the same motion in four other leaves only. 

 This rj'thmical tremor was strong enough to afiect leaves of other 

 plants in the immediate neighborhood Daily observations con- 

 vinced him that the motions of the Colocasia were not regularly 

 periodical. Sometimes they would last all day and through the 

 night; but generally they commenced at nine in the morning, and 

 continued until noon. Not unfrequently the plant would remain in 

 a state of perfect rest for days, and even whole weeks. This 

 induced Mr. Lecoq to attach a few light bells to the plant, in order 

 to be warned of the approach of the paroxysm. On one occasion 

 it began two hours after midnight, and continued nearly the whole 

 morninsr. The bells tinkled, and the leaves were found to make 

 between one hundred and one hundred and twenty pulsations per 

 minute. The fits were exceedingly violent on several other occa- 

 sions. On the second of March last, although the temperature of 

 the hot-house had fallen to seven degrees C, i. e., 44.6 degrees F., 

 the plant seemed to be laboring under a fit of ague, and the pot 

 containing the plant, and weighing about ten kilogrammes, shook 

 so that the hand of a man could hardly steady it. The rythmical 

 ti'cmor was likewise communicated to the fine leaves and clusters 

 of flowers of several plants in close proximity. Mr. Lecoq cannot 

 explain the cause of this tremor, but he thinks himself warranted in 

 not attributing it to the temperature. He suggests the pos^sibility 

 of its being the result of a stoppage in the regular perspiration of 

 the plant. 



ACTINESCENCE. 



M. Carey Lea, of Philadelphia, has published in the June num- 

 ber of The Philadelphia Photographer, a new and plausible theory 

 to explain the nature of the latent image produced by the action 

 of light. It is well known that certain bodies exposed to a brii^ht 

 light, and afterward removed to the dark, have power to emit a 

 distinct light. The action, lasting in some cases only a few hours, 

 and in others several days, is called phosphorescence. Another 

 class of compounds have the power of changing the refrangibility 

 of light in such a manner that the most refrangible rays, which, 



