Daily movement due to tHermo-GeotropIsm 557 



(4) that the weight of the plaut-organ as such, has little 

 effect on the diurnal curve, since an inverted plant conti- 

 nues for a few days to exhibit the periodic movement, in 

 spite of the antagonistic effect of weight. A different 

 experiment will be described (see p. 582) where the effect 

 of weight was completely neutralised and the plant-organ 

 gave, nevertheless, the normal diurnal curve. 



I have also shown that the diurnal movement i.-^ 

 determined by the modifying influence of temperature on 



Fig. 200. — Diurnal record of inclined palm tree, of geotropically curved 

 procumbent stem of Trop(eolwn and the dia-geotropic leaf of palm. Note general 

 similarity between diurnal curve of plants and the thermographic record 



geotropic curvature. Rise of temperature opposes or 

 neutralises the geotropic curvature ; fall of temperature, on 



