MOVEMENT IN PLANTS. 239 



moist chamber of some kind so that the air about the cut 

 shoots is kept saturated. Keep some of the cut shoots in 

 darkness, others in the light. After two or three days, 

 note that in both cases the shoot has made several free 

 spirals, the lower (older) being steeper than the upper 

 (younger). In vigorously growing intact plants these 

 coils would have become more or less completely smoothed 

 out owing to growth after coiling, but in cut shoots the 

 coils persist because the vigour of the plant is greatly 

 reduced. 



321. Influence of Thickness of Support. Place 

 supports of different thicknesses beside different Runner 

 plants in separate pots. All except the thinnest supports 

 can be made by rolling paper or cardboard into tubes and 

 tying them at intervals with string ; for thinner supports, 

 use wooden sticks ; for the thinnest, stretched strings, tied 

 to the base of the stem below and to some convenient 

 support above, e.g. a shelf, or a ~| -shape made of two 

 pieces of wood (the long upright piece lashed to the pot). 



Note that the Runner will not twine round a support 

 more than about 10 cm. in diameter (probably because the 

 support is not curved enough to enable the stem to hold 

 on while the growing free end swings round the support), 

 but it twines readily round a very thin support. It has 

 already been noted that the upper coils made round a 

 support are relatively flat, while the lower ones are steeper 

 owing to the fact that growth occurs after coiling. Note 

 that the thinner the support the steeper are the coils, i.e. 

 the greater is the erecting of the stem; with thick 

 supports, the application of the older coils to the support 

 takes place early, the erecting of the internodes soon stops, 

 and the permanent coils are therefore less steep. 



322. Change from thick to thin Support. Tie a 



Runner to the support 3 cm. in diameter, and when the 

 stem has made a few coils round it replace the support by 

 a much thinner one, say 5 mm. in diameter. Note care- 

 fully the appearance of the coils, making a sketch. In a 

 few days at least the younger of the coils formed round 



