43 TERRESTRIAL ADAPTATIONS. 



this it again becomes erect, the globe being now 

 a fruit filled with fertile seeds. 



The positions in all these cases depend upon 

 the length and flexibility of the stalk which sup- 

 ports the flower, or in the case of the Euphorbia, 

 the germen. It is clear that a very slight altera- 

 tion in the force of gravity, or in the stiffness of 

 the stalk, would entirely alter the position of the 

 flower cup, and thus make the continuation of 

 the species impossible. We have therefore here 

 a little mechanical contrivance, which would 

 have been frustrated if the proper intensity of 

 gravity had not been assumed in the reckoning. 

 An earth greater or smaller, denser or rarer than 

 the one on which we live, would require a change 

 in the structure and strength of the footstalks of 

 all the little flowers that hang their heads under 

 our hedges. There is something curious in thus 

 considering the whole mass of the earth from 

 pole to pole, and from circumference to centre, 

 as employed in keeping a snowdrop in the posi- 

 tion most suited to the promotion of its vegetable 

 health. 



It would be easy to mention many other parts 

 of the economy of vegetable life, which depend 

 for their use on their adaptation to the force of 

 gravity. Such are the forces and conditions 

 which determine the positions of leaves and of 

 branches. Such again those parts of the vege- 

 table constitution which have reference to the 



