268 



THE LIFE OF THE PLANT 



The mimosa and the catchfly are instances of plants 

 capable of manifesting movements in response to the 

 slightest external stimulus ; but here is also a plant in 

 which movements take place without any external 

 stimulus whatever Desmodium or Hedysarum coming 



from the West Indies and 

 belonging to the so-called 

 Papilionaceae and therefore 

 akin to our bean, clover, and 

 other plants. Imagine that, 

 of the three leaflets which 

 form the compound leaf of 

 the clover, the uppermost 

 were to become greatly 

 elongated and the two side 

 ones were but slightly devel- 

 oped so that they were 

 much smaller than the 

 third. Such is the leaf of 



FIG. 78. 



FIG. 79, 



Desmodium, shown in fig. 79. If now we take our stand 

 on a bright hot day before this plant, which is often 

 grown in our hot-houses, we shall notice in less than a 

 minute a slight shudder passing here and there over its 



