DIURNAL MOVEMENT OF M/MOf:A 597 



till about 9 p.ni., after which the leat erects itself 



under thermo-geotropic action of falling temperature, the 



maximum erection being attained at the thermal-dawn at 

 a bout 6 a.m. 



SUMMARY. 



The very complex type of nyctitropic movement of 

 the primary petiole of Mimosa results from the combined 

 effects of thermo-geotropism and phototropism. 



With the exception of a small portion of the curve in 

 the evening, the diurnal curve of Mi?nosa is similar to 

 the standard thermo-geotropic curve, where the leaf exhibits 

 an erectile movement from thermal-noon to thermal- 

 dawn, and a fall from thermal-dawn to thermal-noon. 



Investigations show that the leaf of Mimosa has an 

 autonomous movement of its own, which persists through- 

 out twenty-four hours. 



The torsional response of Mimosa exhibits a diurnal 

 variation similar to that exhibited by the leaf in normal 

 position. 



The leaf of Cassia alata exhibits a diurnal movement 

 of the same type as that of Mimosa. 



The spasmodic fall of the leaf towards evening is not 



due to the increased mechanical moment caused by the 



forward position of the sub-petioles. The record of the 



leaf with amputated sub-petioles exhibits the sudden fall 

 in the evening as that of the intact leaf. 



The evening fall of the leaf of Mimosa is shown to 

 be due to the post-maximum after-effect of light, which 

 causes an 'over-shooting ', the leaf undergoing a fall 

 below the position of equilibrium. 



B. S. Press— 5-11-1910— 19754J—75U—R. DS. 



