96 WONDERS OF ORGANIC LIFE. 



lotus seeds, and watched with interest the 

 progress of the plants. One of these plants 

 developed two flowers. On visiting them in 

 the evening, to his surprise the flowers had 

 apparently vanished, and as his attempt to dis- 

 cover them was in vain, he concluded that some 

 one had plucked them. On returning in the 

 morning, the two flowers had again made their 

 appearance, but in the evening he found that 

 they had again vanished. He now examined 

 the plants with care, and found the flowers 

 concealed by the leaflets, which, on the approach 

 of darkness, had become attracted to each other, 

 and enshrouded the flowers from view. Struck 

 with this circumstance, he took a lantern in his 

 hand and visited his flower-beds ; what was his 

 astonishment to find them no longer with ex- 

 panded petals ! A change had passed over them ; 

 they were folded up ; and thus he made the 

 discovery of the sleep of plants. 



As a general rule, it may be stated that on 

 the approach of night flowers close ; the leaves 

 of plants become more erect, fold themselves 

 together, and lose in a great measure their vital 

 irritability — a change which is very marked in 

 the leaves of the sensitive plant, the irritability 

 of which retires from the leaf to the petiole or 

 leaf-stalk. At this time, that is during the 

 hours of darkness, a very remarkable change 

 takes place in the functions of plants ; during 

 the day they absorb carbon from the atmo- 

 sphere, and exhale oxygen, but during the 

 night they absorb oxygen and exhale carbon. 



