OF RESTING. 327 



post they employ, wTiich is often a point of subordi- 

 nate interest, although generally regarded as of the 

 first importance. If but little progress has yet been 

 made by art in altering the time of flowering of parti- 

 cular races, so as to invert their seasons, this is cer- 

 tainly very far from being beyond the reach of attain- 

 ment ; and there is apparently no more reason why a 

 Chinese Chrysanthemum should not be compelled to 

 flower at midsummer instead- of November, or a 

 Dahlia at Christmas, than that Vines and Strawberries 

 should ripen fruit in February. The great difficulty 

 to contend against in obtaining winter flowers is want 

 of light ; but, by the employment of slender iron sash- 

 bars and large glass, a sufficient amount of this im- 

 portant vital agent may be obtained in England even 

 at that season of the year. 



But it is not merely the periodical rest of winter and 

 summer that plants require ; they have also their 

 diurnal repose : night and its accompanying refresh- 

 ment are as necessary to them as to animals. In all 

 nature the temperature of night falls below that of 

 day, and thus one cause of vital excitement is dimi- 

 nished ; perspiration is stopped, and the plant parts 

 with none of its aqueous particles, although it con- 

 tinues to imbibe them by all its green surface as well 

 as by its roots ; the processes of assimilation are sus- 

 pended ; no digestion of food and conversion of it 

 into organised matter takes place ; and, instead of 

 decomposing carbonic acid by the extrication of oxy- 

 gen, they part with carbonic acid, and rob the air of 

 its oxygen, thus deteriorating the air at night, al- 



