36 TERRESTRIAL ADAPTATIONS. 



motions above described, do not depend alto- 

 gether on external circumstances. 



Some curious experiments on this subject were 

 made by Decandolle. He kept certain plants 

 in two cellars, one warmed by a stove and 

 dark, the other lighted by lamps. On some 

 of the plants the artificial light appeared to 

 have no influence, (convolvulus arvensis, convol- 

 vulus cneorum, silene fruticosa,} and they still 

 followed the clock hours in their opening and 

 closing. The night-blowing plants appeared 

 somewhat disturbed, both by perpetual light and 

 perpetual darkness. In either condition they 

 accelerated their going so much, that in three 

 days they had gained half a day, and thus 

 exchanged night for day as their time of open- 

 ing. Other flowers went slower in the artificial 

 light (convolvulus purpureus). In like manner 

 those plants which fold and unfold their leaves 

 were variously affected by this mode of treat- 

 ment. The oxalis stricta and oxalis incarnala 

 kept their habits, without regarding either arti- 

 ficial light or heat. The mimosa leucocephala 

 folded and unfolded at the usual times, whether 

 in light or in darkness, but the folding up 

 was not so complete as in the open air. The 

 mimosa pudica (sensitive plant), kept in darkness 

 during the day time, and illuminated during 

 the night, had in three days accommodated 

 herself to the artificial state, opening in the 



