SECT. II. IRRITABILITY. 45Q 



an hour afterwards it rose again to 135, and upon 

 being touched a second time fell again also to 80; 

 an hour and a half afterwards it rose to 145, and 

 upon being touched fell to 135, where it remained 

 till five o'clock in the evening, when upon being 

 touched it fell to 1 10. Hence it follows that the 

 susceptibility is greatest in the morning, or during 

 the heat of the day ; but the leaf recovers itself 

 sooner or later according to the vigour of the plant, 

 the season of the year, and temperature of the at- 

 mosphere, as well as the hour of the day at which 

 the experiment is made ; though it does not always 

 recover itself in the same way: for sometimes the 

 common foot-stalk recovers first, sometimes the 

 lateral foot-stalk, and sometimes the leafits them- 

 selves. 



The leaves of Diontea Muscipula, or Venus 1 nionaea 

 Fly-trap, are also extremely susceptible to the action i a> usclpl1 " 

 of accidental stimuli. They are all radical and ap- 

 proaching to battledore-shaped, with a sort of cir- 

 cular process at the apex, which is bisected by a 

 midrib and ciliated with fine hairs like an eye-lash : 

 this circular process is the seat of irritability,, which, 

 if it is touched with any sharp-pointed instrument, 

 or if an insect but alights upon it, the segments im- 

 mediately collapse and adhere so closely, that the 

 insect is generally squeezed to death in its grasp ; or 

 at the least detained a prisoner. 



A similar susceptibility to the action of accidental Drosera, 

 stimuli has been observed in the leaves of the seve- 



