G YRA TION OF PLA NTS. 1 65 



with advantage. There arc some plants which as the 

 flowers fade point their ovaries downwards, and then 

 by the curvature or lengthening of the peduncle, these 

 •ovaries are made to enter the ground and mature 

 their seeds in the earth. The explanation which is 

 offered to account for such movements is that these 

 parts are more than ordinarily sensitive to gravitation, 

 and that it is " geotropism " by which such phenomena 

 should be called, because of their turning to the earth, 

 as " heliotropism " is applied to those which turn 

 towards the sun. Whatever the explanation may be, 

 the phenomena are interesting as exhibiting a curious 

 type of movement of plants. 



We will commence with a species of clover 

 {Trifoliinn siibterranciim) which is indigenous to the 

 .south of England, and therefore of more interest 

 than an exotic would be. For the details of its 

 burying propensities we must again follow the lucid 

 narrative of Mr. Darwin, but somewhat condensed. 

 " The flower-heads of this plant produce onl)'- three 

 or four perfect flowers. All the other flowers are 

 -abortive and modified into rigid points. After a 

 -time five long elastic claws which represent the 

 divisions of the calyx are developed on their summits. 

 As soon as the perfect flowers wither they then bend 

 downwards, as the peduncle stands erect, and closely 

 surround its upper part. The imperfect flowers, 

 which are the central ones in the flower-heads, 



