210 HERBERTS. [CH. VIII 



first be gently stroked on both faces with a dissecting 

 needle or mounted bristle. No movement occurs, but the 

 filament springs in at once when touched on its inner face 

 just below the anther. The outer surface of the filament 

 is not sensitive except at its extreme base. To make 

 sure of this the petals should be dissected off, an 

 operation which requires a little care, and the specimen so 

 prepared should be placed on wet filter-paper under a 

 watch-glass for 10 minutes to recover irritability. Under 

 a simple lens it is now easy to touch the filament in any 

 part. 



The filaments apparently begin to recover from the 

 effect of a touch at once, at any rate a considerable 

 amount of return towards the resting position is visible 

 in 1 or 2 minutes, and in 5 or 10 minutes recovery is 

 complete. 



The stamens may be irritated separately, no trans- 

 mission from one to the next takes place. By applying 

 the tetanising current they may be made to close simul- 

 taneously: we simply wrap one wire round a small twig 

 of Berberis and touch the stigmas with the other wire. 

 Or a single flower may be cut off and held by one of the 

 wires stuck into the pistil, the other wire being applied 

 to the base of the flower outside. 



(243) Berberis : effect of chloroform. 



Gather a flower carefully with a pair of forceps, test 

 its irritability by touching a single filament and place it 

 floating in a watch-glass of water. Add a couple more 

 flowers similarly treated and place the watch-glass under 



