THEORY OF NATURAL SELECTION. 233 



in'lependently acquired it, and cannot have inherited it from 

 a common progenitor. Hence, I was led to predict that 

 some slight tendency to a movement of this kind would 

 be found to be far from uncommon with plants which did 

 not climb; and that this had afforded the basis for natural 

 selection to work on and improve. When I made this pre- 

 diction, I knew of only one imperfect case, namelv, of the 

 young flower-peduncles of a Maurandia which revolved 

 slightly and irregularly, like the stems of twining plants, 

 but without making any use of this habit. Soon afterward 

 Fritz Miiller discovered that the young stems of an Alisma 

 and of a Linum — plants which do not climb and are widely 

 separated in the natural system — revolved plainly, though 

 irregularly; and he states'^ that he has reason to suspect 

 that this occurs with some other plants. These slight 

 movements appear to be of no service to the plants in ques- 

 tion; anyhow, they are not of the least use in the way of 

 climbing, which is the point that concerns us. Neverthe- 

 less we can see that if the stems of these plants had been 

 flexible, and if under the conditions to which they are ex- 

 posed it had profited them to ascend to a height, then the 

 habit of slightly and irregularly revolving might have been 

 increased and utilized through natural selection, until they 

 had become converted into well-developed twining species. 

 With respect to the sensitiveness of the foot-stalks 

 of the leaves and flowers, and of tendrils, nearly the 

 same remarks are applicable as in the case of the revolv- 

 ing movements of twining plants. As a vast number of 

 species, belonging to widely distinct groups, are endowed 

 with this kind of sensitiveness, it ought to be found in 

 a nascent condition in many plants which have not be- 

 come climbers. This is the case: I observed that the 

 young flower-peduncles of the above Maurandia curved 

 themselves a little toward the side which was touched. 

 Morren found in several species of Oxaiis that the leaves 

 and their foot-stalks moved, especially after exposure to a 

 hot sun, when they were gently and repeatedly touciied, or 

 when the plant was shaken. I repeated these observations 

 on some other species of Oxaiis with the same result; in 

 some of them the movement wjis distinct, but was best 

 seen in the young leaves; in others it was extremely slight. 

 It is a more important fact that according to the high 



