Cause of Motion in Plants. 359 



on the under, and the other on the upper, side. Both imme- 

 diately became slightly inclined towards the entire side. The 

 effect was still more marked on the next day; and on the 

 third they were both " nodding," as it were, towards the un- 

 injured side. 



Exp. 6. (Sept. 15.) — Two stems of the Jerusalem Artichoke 

 were tied down horizontally, and all leaves removed except 

 the terminal bunch. 



In fig. 2. several notches were made in the upper side, and 

 it became immediately slightly bent downwards. In fig. 3. 

 the notches were made in the lower side, and it retained its 

 position unchanged. Next day (Sept. 16), fig. 2. was much 

 more curved downwards, and fig. 3. distinctly arched up- 

 wards. On the 17th the extremity of fig 3. was again di- 

 rected upwards. The other was still horizontal. 



Sept. 21. That notched on the under side (fig. 3) was 

 curved more than enough to make its head erect. The other, 

 notched on the upper side, (fig. 2.) was now almost upright, 

 but rather less arched than the first.) 



Fig. 2. Fig. 3. 



Exp. 7. — A very young stem of Jerusalem Artichoke was 

 tied down, and the stem then notched on the upper side. 

 The notches were made near together, and pretty deep, the 

 leaves having been previously removed. The head imme- 

 diately hung downwards. In twelve days it was cut down. 

 Though the position was somewhat changed, its power of 

 erecting itself seemed to have been destroyed. The notched 

 part still inclined downwards, and not even the apex was 

 turned upwards. 



IV. Pa?is which are not divergent are not capable of Motion. 



a. The living sprays of all trees, and all herbaceous steins 

 which have become rigid and acquired ligneous matter, are, 

 I believe, invariably incapable of raising themselves up by 

 curving, if laid down, and they are not divergent on division. 



b. Many plants which whilst young were capable of mo- 

 tion and divergent on division, lose the property of diver- 



