36 TTIRRESTRIAL ADAPTATIONS.

and the period of the motions above described, do not depend altogether 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. Q11 some of the plants the artificial light appeared to have no influence, (convolvulus arveusis, convolvulzis cneo- rum, silene jiwzticosrz) and they still followed the clock hours in their opening and closing. The night-blowing plants appeared somewhat dis- turbed, both by perpetual light and perpetual darkness. In either condition they accelerated their ‘glfinrr s0 much, that in three days they had

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gained half a day, and thus exchanged night for day as their time of opening. Other flowers u-cnt slower in the artificial light (conrolvulzls purpli- reus). In like manner‘ those plants which fold and unfold their leaves were variously effected by this mode of treatment. The oazalis stricta and omalis l-IICIUVIHH! kept their habits, without regarding either artificial light or heat. The mimosvt /('ll(‘()(‘(’])/l!ll(t folded and unfolded at the usual times, whether in light or in dzirkness, but the folding up xvas not so complete as in the open air. The 2nimo.sr1 [H/(UCU (sensitive plant), kept in darkness during the day time, and illuminated during the night, had in three days accommodated herself to the artificial state, (vpening in the