82 MOTIONIN 



Bat in some of the species of Mimosa or Sensitive 

 Plants, the slightest touch of the hand will produce 

 a sudden and very considerable change in the posi- 

 tion of the leaves, as they will immediately fold them- 

 selves together, and if the touch be repeated, the 

 leaf-stalks will fall and bend themselves toward the 

 stem. A strong wind or heavy rain will produce the 

 same effect, and those kinds which grow in countries 

 where there is a long continuance of rain, close their 

 leaves upon its approach, and are seldom fully ex- 

 panded until the return of fair weather. 



The leaves of the common sensitive plant will par- 

 tially close at evening, and remain so until the light 

 of day again causes them to expand ; and when ex- 

 posed to sudden cold during the daytime, they will 

 fold themselves face to face, so as to allow as little as 

 possible of the upper surface to remain open to the 

 air. 



The Venus Fly-trap is also an example of motion ; 

 the leaves are very curiously constructed. At the 

 extremities are spread out two wide and rounded 

 lobes, each armed upon the margin with rows of 

 spines, or rather stiff hair -like processes, locking 

 into each other when they meet, which always occurs 

 when irritated. The upper surface of these lobes is 

 covered with minute glands, which evidently con- 

 tain a liquid attractive to insects, as they fre- 

 quently resort to the plants ; but no sooner do they 

 alight upon the leaves, and their little feet irritate 

 them, than the two lobes instantly fold together, 

 squeezing the insect to death. The leaf seldom opens 



