POWER OF MOVEMENT IN PLANTS. 305 



compass, and this wliolly irrespective of external influences ; 

 and the twining around a support is the direct consequence 

 of the circumnutation. Most tendrils freely circumnutate, 

 and thereby are enabled to reach the object which they grasp. 

 Most tendrils (and in certain cases some other parts) are 

 very obviously sensitive to external contact or irritation, to 

 which they respond by movement and change of form, and 

 thus they grasp or do other advantageous acts. Some move- 

 ments, especially of leaves, occur with regularity upon the 

 access of light, others with its withdrawal ; a few, such as the 

 small leaflets of Desmodium gyraiis, proceed irrespective of 

 night and day. The specification need not be extended. The 

 general facts in all their great variety are familiar to scientific 

 readers. The inquiry of this volume is as to their ground 

 and origin, or, as in this connection we should rather say, 

 their development and history. For instance, circumnutation 

 gives rise to twining and gives efficiency to other ways of 

 climbing. But Darwin is bound to suspect, and even to show, 

 that circumnutation is not a special endowment of the stems 

 and tendrils of climbing plants, but rather a more developed 

 manifestation of a general faculty. And the same is to be 

 said of the movements of tendrils and leaves, or their appen- 

 dages, whether automatic or in response to external irritation 

 or stimulus. All this is what the experimental researches 

 detailed in this volume undertake to ascertain and have satis- 

 factorily made out. 



An abstract of the volume might be somewhat tedious, and 

 is certainly unnecessary for biological readers, who are sure 

 to possess and study it. But the gist is readily to be gathered, 

 without running through the iterated details or scanning 

 many of the illustrative and curious figures which record the 

 movements under investigation, by the simple perusal of the 

 introduction and of the concluding chapter, in which the mat- 

 ter of the volume is summed up. 



The sum and substance of the case is, that all these powers 

 and faculties are manifested in the seedling immediately upon 

 germination, and most of them are then remarkably exem- 

 plified. The caulicle or initial portion of stem below the 



