Petiole- Pulvinus Preparations of Mimosa pudica. 



231 



the lower half of the pulvinus. The excitability of the lower half is eighty 

 times greater than that of the upper. 



Chemical agents induce characteristic changes in excitability. Hydrogen 

 peroxide acts as a stimulant. Barium chloride renders the recovery incom- 

 plete ; but tetanisation temporarily removes the induced sluggishness. Acids 

 and alkalis induce antagonistic reactions, abolition of excitability with alkali 

 taking place in a contracted, and with acid in an expanded, condition of the 

 pulvinus. 



The responses exhibit fatigue when the period of rest is diminished. The 

 passage of constant current is found to remove the fatigue. Eesponse is 

 enhanced on exposure to light, and diminished in darkness. Light is shown 

 to exert a direct stimulating action on the pulvinus, independent of photo- 

 synthesis. Application of glycerin on the petiole enhances the velocity of 

 transmission and the intensity of the transmitted excitation. 



Injury caused by cut or section of the petiole induces a variation in the 

 conducting power. Two different effects are produced, determined by the 

 tonic condition of the specimen : in normal specimens injury depresses the 

 conducting power, in sub-tonic specimens it enhances it. 



The records given are photographic reproductions of the original tracings. 



I take this opportunity of acknowledging the special facilities for carrying- 

 out these researches that have been afforded me by the Hon. P. C. Lyon, 

 C.S.I., Minister in charge of Education, Government of Bengal. 



