l82 



OUTLINES OF PLANT LIFE. 



the morning, the day position is assumed. The cutting off 

 of light artificially from any of these plants causes them 



Fig. T36.— Photeolic movements. «, leaf of a mimosa in day position; a' y the same in 

 ni^lit position. /', leaf of Coronitta varia in day position ; b' ^ the same in night po- 

 sition, c, leaf of A morpha /rut i cosa in day position ; c\ the same in night position. 

 dy leaf of Teiragonolobus in day position ; d' ^ same in night position. — After Kemer. 



within a short time to assume the nocturnal position. Their 

 purpose is not certainly known. 



EXERCISE XLIV. 



To show effect of intensity of light as a stimulus on certain leaves. 



Observe the position of the leaflets of white, red, or sweet clover, bean, 

 locust, or oxalis at 3 P.M., 6 p.m., at dusk (or after nightfall by using a 

 lantern) and at 8 A.M. In the morning darken with a box a plant show- 

 ing these movements. After an hour or two, observe the position of leaf- 

 lets. 



256. Contact movements. — Some organs are sensitive to 

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



