240 RESEARCHES ON IRRITABILITY OF PLANTS 



conducting-tissue of Biophytum on account of the presence 

 of the lateral motile-leaflets. 



I will now describe experiments carried out on Biophy- 

 tum with feeble and strong currents, and show how they 

 throw light on parallel experiments with nerve-and-muscle 

 preparation of animal. In Biophytum the excited leaflets 

 are indicated by dark shading, which will also clearly 

 exhibit the extent of excitatory overflow. The point of 

 initiation of excitation, and direction of transmission, are 

 indicated by arrows. 



Effect of Feeble Current 



In the nerve-and-muscle preparation it is known that (i) 

 excitation takes place at the make of descending current ; 



(2) excitation also occurs at the make of ascending current ; 



(3) no excitation occurs at the break of descending, (4) or 

 ascending, currents. Accounts of parallel experiments with 

 Biophytum will now be described : — 



(i) Make of descending current. — The kathode is proximal 

 to the extra-polar or terminal leaflets to the left. At 

 make, excitation is seen to be initiated only at K, the two 

 waves proceeding in opposite directions. Five pairs of 

 leaflets thus fall in the extra-polar and three pairs in the 

 intra-polar regions. This excitatory overflow in the intra- 

 polar region cannot be observed in the animal nerve on 

 account of absence of a visible indicator. 



(2) Make of ascending current. — In fixing our attention to 

 the terminal or extra-polar leaflets to the left of A, we find 

 occurrence of excitation corresponding to the excitation of 

 muscle at the make of the ascending current. That the 

 excitation was really initiated at the distal kathode, and 

 traversed without hindrance through the feeble anode, will 

 clearly be seen from the serial closure of the leaflets initiated 

 at K. Eight pairs of leaflets underwent excitatory fall to 

 the left, and one pair to the right of K. 



(3 and 4) Break of ascending and descending currents. — 



