8 INTKODUCTION. 



introdu3cd a superfluous number of diagrams; but they take 

 up less sijace than a full description of the movements. Almost 

 all the sketches of plants asleep, &c., were carefully drawn 

 for us by Mr. George Darwin. 



As shoots, leaves, &c., in circumnutating bend more and 

 more, first in one direction and then in another, they were 

 necessarily viewed at different times more or less obliquely; 

 and as the dots were made on a flat surface, the apparent 

 amount of movement is exaggerated according to the degree 

 of obliquity of the point of view. It would, therefore, have 

 been a much better plan to have used hemispherical glasses, 

 if we had possessed them of all sizes, and if the bending part 

 of the shoot had been distinctly hinged and could have been 

 placed so as to have formed one of the radii of the sphere- 

 But even in this case it would have been necessary afterwards 

 to have projected the figures on paper; so that complete 

 accuracy could not have been attained. From the distortion 

 of our figures, owing to the above causes, they are of no use 

 to any one who wishes to know the exact amount of movement, 

 or the exact course pursued; but they serve excellently for 

 ascertaining whether or not the part moved at all, as well as 

 the general character of the movement. 



In the following chapters, the movements of a con- 

 siderable number of plants are described ; and the 

 species have been arranged according to the system 

 adopted by Hooker in Le Maout and Decaisne's ' De- 

 scriptive Botany.' No one who is not investigating 

 the present subject need read all the details, which, 

 however, we have thought it advisable to give. To 

 save the reader trouble, the conclusions and most of 

 the more important parts have been printed in larger 

 type than the other parts. He may, if he thinks fit, 

 read the last chapter first, as it includes a summary 

 of the whole volume ; and he will thus see what 

 points interest him, and on which he requires the 

 full evidence. 



Finally, we must have the pleasure of returning oui 



