RECORD OF STEM AND LEAF 237 



characteristic only of Palms, or whether they can also 

 be detected in other plants under parallel conditions. In 

 answer to this, I first experimented with the procumbent 

 stem of a young plant of Mimosa (fig. 137). 



Diurnal Movement of Stem of Mimosa 



Experiment 128. — The stem was nearly horizontal and 

 therefore subjected to the stimulus of gravity. The diurnal 

 records of the movement of the stem and of the variation 

 of temperature showed that while the temperature rose 

 from noon to 2.30 p.m., the Mimosa stem exhibited a fall. 

 The temperature fell after the thermal noon, this being 

 attended by rise of the stem, the lag of response being 

 about an hour. The erectile movement continued wdth the 

 fall of temperature till about 6 next morning. After this 

 the temperature began to rise and the stem responded by 

 a fall. As in all cases hitherto considered, the erectile 

 movement of the plant occurred from thermal noon to 

 thermal dawn, the fall taking place from thermal dawn to 

 thermal noon (fig. 137). The diurnal record of the pro- 

 cumbent stem of Mimosa is thus in every way similar to 

 that of the Sijbaria Palm Tree. 



If it be true that induction of anisotropy by the geotropic 

 stimulus renders the stem of the Palm effective to respond 

 to variation of temperature by the characteristic up and 

 down movement, then ordinary stems curved under the 

 action of gravity, as well as dia-geotropically outspread 

 leaves of plants, might also be expected to exhibit such 

 movements. 



Diurnal Records of Stem and Leaf 



Experiment 129. — I took diurnal records of a geotropically 

 curved stem of Tropaeolum and of a dia-geotropic leaf 

 of Dahlia for two days in succession. The thermal record 

 shows the usual fall of temperature after thermal noon, from 



