44/1 CHARACTER OF VEGETABLE VITALITY. CHAP. XI. 



inferior side of the leaf-stalk, the terminal lobe, if 

 the leaf is furnished with one, folding itself back till 

 it reaches the first pair ; or the two side lobes, if the 

 leaf is trifoliate, as in the case of common Clover, 

 which seems to have been first observed by the 

 daughter of Linnaeus. So also the leaflets of the 

 False Acacia and Liquorice hang down during the 

 night, on each side of the mid-rib, but do not meet 

 beneath it. The leaves of Mimosa pudica fold 

 themselves up along the common foot-stalk so as to 

 overlap one another. But, perhaps, this effect is 

 produced partly by the agency of moisture as it is ac- 

 celerated by dews and rains, and may even be oc- 

 casioned by artificial watering : or perhaps such 

 leaves as fold themselves up in the above man- 

 ner may require an interval of rest, which they thus 

 obtain, after having been exposed throughout the 

 day to the stimulus of light. And if so, then Linnaeus 

 has not without propriety designated the above 

 phenomenon by the appellation of The Sleep of 

 Plants. 

 Influence The expansion of the flower is also effected by the 



Sower". acti n f ]i ht - Man y P lantS d n0t ful ty ex P an(i 

 their petals except when the sun shines ; and hence 



alternately open them during the day and shut 

 them up during the night. This may be exemplified 

 in the case of papilionaceous flowers in general, 

 which spread out their wings in fine weather to ad- 

 mit the rays of the sun, and again fold them up as 

 the night approaches. It may be exemplified also 



6 



