SPONTANEOUS MOVEMENTS IN PLANTS. 839 
become wonderfully strong and durable. The tendril has 
done its work, and done it in an admirable manner.” 
The phenomenon known as Sensitiveness is of by no 
means uncommon occurrence in the vegetable kingdom. It 
consists of a sudden movement of the leaf, a portion of the 
flower, or the whole plant, on contact with, or even on the * 
approach of, a foreign body. One of the most familiar ex¬ 
amples is that of the Sensitive Plant, Mimosapudica and sen- 
sitiva, in which three distinct movements are observable when 
the leaf is touched by the hand or the warm breath. First, 
the numerous leaflets close in pairs, bringing their upper 
faces together, and also inclining forwards; then the four 
branches of the leaf-stalk, which were outspread like the rays 
of a fan, approach each other; at the same time the main leaf¬ 
stalk turns downwards, bending at its joint with the stem. 
The explanation offered in one of our best botanical text¬ 
books of this phenomenon is as follows :—“ There is a swell¬ 
ing at the base of the petiole, the cells of which constitute, 
as it were, two springs acting in contrary directions, so that 
if the one from any cause be paralysed, the other pushes the 
leaf in the direction of least resistance. These springs, if 
they be so called, are set in action by the rush of fluid cre¬ 
ating a turgid state of the one set of cells and an empty state 
of the other. What circumstances regulate the turgescence 
are only imperfectly known.” It will be obvious that even 
if this is correct as a statement of facts, it offers no real ex¬ 
planation of the phenomenon ; for it is quite as difficult to 
understand how the mere approach of the hand, which gives 
rise to a sensitiveness commencing, it will be remarked, at 
the extremity of the leaf, will account for a Cf turgescence ” of 
the springs at the base of the leaf, which then causes the 
movement. It should be observed also that we are unaware 
of any use which these movements are to the plant. Similar 
sensitiveness occurs in the leaves of some other leguminous 
plants, in several species of Oxalis, &c. M. Bert has ob¬ 
served that the sensitiveness is destroyed by the continual 
application of chloroform, and also by placing the plant con¬ 
stantly in the dark or in green light. 
Similar movements to that of the Sensitive Plant, but oc¬ 
curring spontaneously, may be observed in other plants. 
Thus, in the Desmodium gyrans , or “ Telegraph Plant,” some¬ 
times grown in our hot-houses, belonging to the same order, 
Leguminosse, the leaf consists of three leaflets, a large cen¬ 
tral, and two smaller side ones. The motion is especially 
observable in the small side leaflets, w r hich on a warm sum¬ 
mer’s day may be seen to rise and fall by a succession of 
