36o TEE POPULAR SCIENCE MONTHLY 



appeared in 1865 and ten years later he revised and enlarged it as a book 

 under the title "The Movements and Habits of Climbing Plants," 

 using, as always, not only his own detailed and extensive observations, 

 but also the published writings of other botanists, among them the paper 

 on tendrils by Hugo de Vries, who was subsequently destined to throw 

 such a flood of light on the phenomena of variation. Darwin grouped 

 climbing plants into twiners, leaf-climbers, tendril-bearers, hook-climbers 

 and root-climbers. He maintained that the climbing habit has been 

 developed to enable vines to reach the light and free air ; tropical forests 

 show conclusively that this is the case. He showed that circumnutation, 

 the bending of growing tips successively to all points of the compass, is 

 a general phenomenon among flowering plants, and he thought it of 

 high importance to them. The sensitiveness of tendrils to external 

 influences interested him deeply and he made many original experi- 

 ments upon them. Following the subject much further, he published in 

 1880 the work entitled "The Power of Movement in Plants," a treatise 

 abounding in records of original observations on seedlings and parts of 

 mature plants, including further studies of circumnutation, of the sensi- 

 tiveness of plants to light and to other forces, and of the phenomena of 

 geotropism and apogeotropism, which he regarded as modified phe- 

 nomena of circumnutation. 



The value of the impulse given by Darwin to botanical investigation 

 in all its branches is beyond estimation ; his power of exact observation 

 and record has seldom been equaled and certainly never excelled; his 

 deductions were highly philosophical and most of them have stood the 

 test of thirty years' inquiry and criticism; he was searching for truth 

 and his absolute honesty in research is plainly evidenced by his repeated 

 criticism of his own conclusions. 



The immense number of plant species which had been described 

 and named, and the lack of any complete index to them led Darwin 

 to provide in his will for complete enumeration of the names of pub- 

 lished species of flowering plants. This great work was prepared at 

 the library of the Eoyal Gardens, Kew, England, and published in 

 1895 in four large quarto volumes, to which several supplements have 

 since been added. This " Index Kewensis " is a great boon to all 

 investigators, and is quite indispensable to those who have to take 

 plant names into consideration. 



