338 THE JOURNAL OF INDIAN BOTANY. 



placed to counter-balance, the weight of the piece. Plate II, fig. 27 

 shows how this was done, and it will be seen that no appreciable 

 curvature took place. In the course of the experiment a lessening 

 of the weight, by loss of evaporated water caused the terminal threads 

 to slacken ; but at the beginning of the experiment, the weight was 

 evenly distributed and the lack of curvature cannot therefore, be 

 due to any pull upwards, at the centre of gravity. 



Since the region of curvature is in the weak still unlignified 

 internodes near the apex (vide figs. 1, 2 and 3) it is clear that the bend- 

 ing moment at the point of curvature due to the comparatively heavy, 

 succulent leaves, will be much greater when these are at the apical 

 end, than if they are at the basal (compare figs. 1 and 2 with 3). 



In another series of experiments living stems of Coleus still 

 attached to the roots, were laid horizontally, the growing point and 

 the first visible internode, being removed as before. Three pairs 

 of plants were used, and in one of each pair, a pair of apical leaves was 

 left, while in the other one or more near the base. Plate II, fig. 19-26 

 show the resulting curvature after 24 hours. It will be seen that no 

 definite relationship, can be established between the amount of curva- 

 ture and the existence or position of leaves Compare Nos. 19 with 

 20, 23 with 24, 21 and 22 with 25 and 26. 



B. The root-forming ' hormones' — Our experiments failed likewise 

 to support Loeb's theory, that root-formation is due to hormones pro- 

 duced in the leaf. Roots were formed freely on the lower side and 

 especially at the region of curvature (figs. 1 and 4) of stems kept 

 damp ; but in no apparent relation with the existence or position of 

 leaves. The presence of water, we found to be a much more impor- 

 tant factor. 



Pieces of stem were placed vertically, in the normal or the revers- 

 ed position, and one end kept damp, by tying a wet rag round it. In 

 every case roots appeared, whether at the upper or lower end, whe- 

 ther at the apical or the basal. This is exactly in conformity with 

 Klebs results (7). 



This occurred also with both isolated and attached leaves of Bryo- 

 phyllum. Roots appeared always in a day or two, at the parts kept 

 wet. Loeb's results (4) of hanging leaves in different positions, 

 which led him to postulate a flow of root-forming substances towards 

 the base of a leaf appear therefore, to have been accidental. In our 

 experiments, leaves were hung in a vertical plane. 



(1) by the petiole 



(2) by a hole in the apical end 



(3) by a hole at one side and 



(4) horizontally by threads through two holes in the lamina. 



