84 LIFE IN NATURE. 



halves of the lateral leaflets exhibit the natural and 

 unimpeded growth of the part. The central leaflet, 

 though resisted equally on both sides , and therefore 

 symmetrical in form, yet has been formed under re- 

 sistance. The free or perfect leaflet would be repre- 

 sented by the union of the two lower halves of the 

 lateral leaflets (see Fig. 9). The difference of this 



Fig. 9. 



Central leaflet, as in nature. Leaf formed by the lower halves 



of the lateral leaflets. 



form from that of the central leaflet indicates the 

 effect of the pressure exerted on the latter by the 

 adjacent parts. 



Or let us pass to another simple object. Tig. 10 

 represents a pea which has been made to germinate 

 in water. The radicle has grown freely into a 

 spiral form ; the plumule has risen up into a curve. 



