1 82 FREAKS OF PLANT LIFE. 



duncles, and only one became within this time at all 

 bowed downwards, and that doubtfully. The weight, 

 therefore, of the pods is not the cause of the bending 

 down. This pot was then brought back into the 

 light, and after three days the peduncles were 

 considerably bowed downwards." 1 The further de- 

 scription only relates to the oscillating or- rotating 

 movement by means of which the pods excavated 

 for themselves saucer-like depressions in sand or 

 sawdust, or were enabled to bury themselves 

 amongst moss, &c. 



The phenomenon of " diurnal sleep " may be illus- 

 trated by two familiar examples. The attributes of 

 this movement consist in turning sideways to the 

 light, so that the edges of the leaves or leaflets being 

 directed towards the sun the surfaces should escape 

 its direct influences. The false acacia, or thorny 

 acacia (Robinia pseudacacia), is a common tree in this 

 country, not uncommon in towns, but more in favour 

 on the Continent than with us. The leaves are com- 

 pound ; that is, they consist of a row of leaflets 

 arranged along each side of a common footstalk. It 

 is well enough known that these leaflets at night 

 are pointed vertically downwards, whereas under a 

 moderate light they are almost horizontal. When 

 the sun shines brightly on these leaves another 



1 Darwin, " Movements of Plants," p. 433. 



