266 THE SECOND BOOK OF BOTANY. 



vines. "When a tendril has effected an attachment, 

 and both ends are fast, how does it continue to coil ? 

 How do the tendrils of grape-vines move in respect 

 to the light ? In what way do they seize the support ? 

 In what way do the tendrils of the Virginia creeper 

 and ivy attach themselves to walls 2 On a sultry day 

 rub gently, with a stick or with the finger, the whole 

 length of a vigorous tendril, and note the effect, and 

 the time in which it is produced. 



TWINEES. Some plants rise by twisting around 

 their support, as in the familiar case of the bean, or 

 the hop, or the morning-glory. The extremity of 

 the stem of a bean, which has grown a foot or two 

 beyond its support, will extend from it in a nearly 

 horizontal direction. If its position at a certain time 

 be noticed, and then, if it be observed again some 

 time afterward, it will be found to have changed 

 place, and to point successively in different directions. 

 The end of the stem thus revolves in a circle round 

 its support, and the same kind of plant always turns 

 in the same direction, although some go with the sun 

 and some against it. The twining is, of course, the 

 simple result of revolving in a circle, for, if the stem 

 reaches away, and is arrested at any point by an ob- 

 stacle, the portion beyond continues to move round 

 in the same direction, and, as it lengthens, it of course 

 twines around the impediment. 



Observe the attitude of a stein of the bean, hop, 

 or morning-glory, that overtops its supports. Mark 

 the position, and observe it again in an hour or 'two 

 afterward. What is the direction taken in each 

 case ? How does temperature affect the result ? Do 

 they move in the night ? Make dots with ink along 



