joo Experiments on Vegetation, 



ful influence was obferved on the deep of the fenfitive plant. 

 Several fenfitive plants, expofed for three days to the conti- 

 nued light of the lamps, opened and clofed each day two 

 hours fooner than the day before; from which it appears that 

 the continuance of light haftened and did not interrupt their 

 movements. When expofed to the fame light during the 

 night, and to obfeurity in the daytime, they exhibited a re- 

 gular progrefs for nearly two days ; after which they ex- 

 panded in the evening and clofed in the morning. Their 

 movements were not deranged by total obfeurity, but they 

 feem to have been retarded by a heat of 6o° to 8o°. A heat 

 of 78 rendered the plant fickly, and deprived it for two days 

 of its fenfibility when touched. 



Thefe facts, according to the author, can be explained 

 Only two ways. We may fay that thefe periodical move- 

 ments are peculiar to the fibres of plants, and that external 

 circumftances are only the Simulants which excite or retard 

 them ; or that the periodical movements continue notwith- 

 standing the change of external circumltances, only on ac- 

 count of the habit acquired by the fibres. This laft expla- 

 nation appears more probable than the other, becaufe we are 

 already acquainted with fome faefs which feem to indicate 

 that plants are fufceptible of habit. But, whatever may be 

 the explanation vve adopt, we nnift admit as the foundation 

 of it the theory of irritability; that is to fay, to acknowledge 

 that vegetables are endowed with a peculiar kind of life or 

 force, in confequence of which their fibres are not afTefted 

 by external bodies, as unqrganifed beings would be from the 

 mere laws of mechanics. 



The EnglifTi journals having announced fome new experi- 

 ments reflecting the theory of Galvanifm, a memoir on which 

 had been prefented to the Royal Society by ProfclTor Volta, 

 thefe experiments have been repeated by C. Robertfon, and, 

 by a commiflion choien by the Inftitute. 



MISCEL- 



