RATE OF TRANSMISSION OF IMPULSES 



of the petiole with the main stem. The angles should be meas- 

 ured exactly with a protractor. The influence of the stimulus 

 may be conducted up or down the stem to other leaves in which 

 it will be transmitted from the bases toward the apices, causing 

 the movement of the petiole first and of the leaflets last. 



The demonstration of reac- 

 tion to shock may also be 

 made with Biophytum sensiti- 

 vum. In this plant the leaves 

 are simply pinnate. A stimu- 

 lus applied to the terminal pair 

 of leaflets is transmitted the 

 length of the rachis only, and 

 does not pass into the other 

 leaves attached to the crown, 



FlG. 3. Biophytum sensitivum. A, 

 A, A, leaflets after mechanical stimulation. 



ordinarily, although Haber- 

 landt 1 demonstrated transmission through stems and flower 

 stalks. A notable feature of the reaction in this plant is the fact 

 that in response to a single stimulation the leaflets close toward 

 each other in pairs through a small arc, and then after a short 

 interval make a second movement in the same direction. 



19, Rate of Transmission of Impulses or Stimulus-effects. With 

 watch in hand snip the terminal pair of pinnules of a normal 

 leaf of Mimosa by means of a pair of scissors or forceps, and 

 note the number of seconds elapsing before each pair of pin- 

 nules closes together as the impulse traverses the midrib, and be- 

 fore the whole leaf falls down by the action of the main pulvinus 

 at its base. Next note the time elapsing before the impulse 

 reaches the leaves above and below the one originally stimulated. 

 Measure the distance from the point at which the stimulus was 

 applied to every point of action and estimate the rate of trans- 

 mission in the different organs. If the stimulus applied does not 



1 Ueber die Reizbewegungen und die Fortpflanzung bie Biophytum. Ann. Jard. 

 Bot. d. Buitenzorg. Second Supplement, p. 33. 1898. See also MacDougal. 

 Transmission of impulses in Biophytum. Bot. Centralb. 77: 297. 1899. 



