TENDKIL-BEAHEKS. 93 



the extremity of a free tendril were to contract quite regularly, 

 it would roll itself up into a flat helix, as occurs with the Cardio- 

 spermum ; but if it were to contract in the least on one side, or 

 if the basal portion were first to contract (as does occur), the 

 long free extremity could not be rolled up within the basal part, 

 or if the tip were held during the contraction, as when a tendril 

 has caught some object, — in all these cases the inevitable result 

 would be the formation not of a helix, but of a spire, such as 

 free and caught tendrils form in the act of contraction. 



Tendrils of many kinds of plants, if they catch nothing, con- 

 tract after an interval of several days or weeks into a close spire ; 

 but in these cases the movement takes place after the tendril 

 has lost its revolving power and has partly or wholly lost its sen- 

 sibility, and hangs downwards ; this, as we shall presently see, 

 is a quite useless movement. The spiral contraction of unat- 

 tached tendrils is a much slower process than that of attached 

 tendrils : young tendrils which have caught a support and are 



spirally contracted may be constantly seen on the same stem with 

 much older tendrils, unattached and uncontracted. In the Echi- 

 nocystis I have seen a tendril with the two later^ branches 

 clasped to twags and contracted into beautiful spires, whilst the 

 main branch which had caught nothing remained for many days 

 afterwards uncontracted. In this plant I once observed a main 

 branch after it had caught a stick become spirally flexuous in 7 h., 

 and spirally contracted In 18 h. Generally the tendrils of the 

 EcJiinocystis begin to contract in from 12 h. to 2i h, after catching 

 something ; whilst its unattached tendrik do not begin to con- 

 tract until two or three or even more days have elapsed after the 

 revolving movement has ceased. I will give one other case : a 

 full-grown tendril of Passijlora qxiadrangularis which had caught 



■ 



a stick began in 8h. to contract, and in 24 h. several spires were 

 formed ; a younger tendril, only two-thirds grown, showed the first 

 trace of contraction in two days after clasping a stick, and in two 

 additional days had formed several spires ; hence, apparently, the 

 contraction does not begin in a tendril until it is grown to nearly 

 its full length. Another young tendril of about the same age 

 and length as the last did not catch any object ; it acquired its 

 full length in four days ; in six additional days it first became 

 flexuous, and in two more days had formed one complete spire. 

 This first spire was formed towards the basal end of the tendril, 

 and the contraction steadily but slowly progressed towards the 

 apex ; but the whole was not closely wound up until 21 days had 



