l88 Influence of Artificial Light on Vegetables. 



objeft which the author firft propofed in his refearches was' 

 to atccrtain the influence which light has on the flcep of the 

 leaves ami flowers of plants. It appears to the author, that 

 regular viciflitude of day and night in the ordinary courfe of 

 things renders any refearches in this refpec.1 exceedingly diffi- 

 cult; and he thinks that they might be rendered much eafier 

 if vegetables were expofed to an artificial light, continued or 

 combined in various ways. For this purpofe he placed fix 

 lamps in a dark cellar, and difpofed them in fuch a maimer 

 that the illuminated plants had only about 66 or 67 degrees 

 of heat, and were fheltered from the fmoke. Thefe fix lamps 

 gave a light equal to 54 tapers. The experiments which he 

 made with this apparatus are as follow: 



Muftard (the myagrum falivum) and creffes, fown, reared, 

 and made to grow, expofed to this artificial light, had a fen- 

 fibly green colour; but their ftalks were a little longer than, 

 thofe which grew in the open air. 



The leaves of different plants put under water, and expofed 

 to the light of thefe lamps, produced no oxygen gas for 

 twenty -four hours j afterwards they putrefied, and formed a 

 deleterious gas. This refult is not aftonifliing, fur fix lamps 

 are not equal to the light of the fun; and it is well known 

 that in the fhadc no oxvgen sras is difengaged. 



Branches of the lime-tree, Jblanum lycoperjlcum, immerfed 

 in water and expofed comparatively to the light of thefe 

 lamps, an obfeure heat of 69' Fah. and the open air during 

 night, attracted much more water in the light than inoblcurity. 

 Branches of the oak attracted little water in the light, and a 

 great deal when expofed to heat. Branches of the fir attracted 

 very little in the light. It would appear that this element 

 has a ftronger aition on vegetables that flied their leaves 

 than on ever-greens. 



The ceffation of fucYion and of tranfpi ration during the 

 night is a real deep common to all plants. This name, 

 however, is given to a particular pofition which the leaves 

 and flowers of certain plants aflume in the night-time. 



Linnaeus diftinguifhes the fdar flowers into three claffes; 



the meteoric, tropical, and equinoctial. C. Decandolle is of 



opinion that to thefe we ought to add the ephemera!, which 



9 flower 



