THE MOVEMENTS OF PLANTS. 



207 



298. Contact movements. Some organs are sensitive to 

 contact, as the leaves of Venus' fly-trap and other related 

 plants. The motor organ in the Venus' fly-trap (figs. 386, 

 205) is the cushion of tissue running along the dorsal side of 

 the leaf between the two lobes. By the sudden variation in 



a 



FIG. 204. Photeolic movements, a, leaf of a mimosa in day position ; a', the same in 

 night position. 6, leaf of Coronilla varia in day position ; />', the same in night po- 

 sition, c, leaf of A morpha fruticosa in day position ; c' , the same in night position. 

 d, leaf of Tetragonolobus in day position ; d' ' , same in night position. After Kerner. 



turgor of some of these cells the two halves ot the leaf are 

 thrown quickly together when one of the six bristles upon its 

 upper surface is touched. The sensitive plant drops one of 

 its leaflets or the whole leaf quickly when stimulated by con- 

 tact, heat, or electricity. The position of the leaves when 



