264 LEISURE-TIME STUDIES. 



irritability displayed by the compound leaves of the Mimosa 

 or sensitive-plants (Fig. 43), the praises of which Shelley 

 has so well sung in his flowing and melodious rhythm. The 

 main leaf-stalk in mimosa gives off four divisions, each of 

 these latter bearing a double row of little leaflets. The 

 leaflets are expanded when the plant is exposed to light, 

 but when darkness comes on, or, more curious still, if the 

 leaf be touched, the leaflets become huddled together on 

 each leaf-stalk, as if in terror and alarm ; and the main leaf- 

 stalk also droops and becomes closely applied to the side of 



FIG. 43. Mimosa fiudica, the sensitive-plant. 



the stem, the entire action reminding one of the cowering 

 aspect of an animal under the influence of strong fear. 

 After all sense of irritation may be presumed to have passed 

 away, or, in the plant's normal state of existence, when the 

 morning light breaks, the leaflets or leaf-stalks once more 

 expand, and present themselves in their normal and un- 

 disturbed condition. But the mimosa is sensitive to stimuli 

 of a kind which affect the animal organisation and animal 



