CLIMBING PLANTS 



35 



any object touched. Again, the base of the stem, even though 

 it reaches nothing round which it can twine, sometimes takes the 

 form of a spiral, thus forming a good foundation for the upper 

 portion as it seeks out a convenient prop. Yet another contrivance 

 to secure the same end may be observed in the Greater Bindweed 

 and some other plants. The stems, faiUng to seciu'e a favourable 

 hold, twine round one another, thus producing a kind of rigid cable 

 for the support of the upper extremities as they revolve in order to 

 find stems round which to form their spirals. 



Should all the methods and contrivances of the twining plant 

 fail it in its attempts to secure an uppermost place among the 

 smTounding herbage or shrubs, it is compelled to trail along the 

 ground. But such a position is most disadvantageous and unnatural 

 to it, and usually results in a 

 stunted and sickly plant that 

 may produce no flowers. 



Most of the twining plants of 

 om- country are of short duration. 

 Many, Uke the Climbing Buck- 

 wheat, are annuals ; while others, 

 as the Hop and the Bindweeds, 

 though they have perennial roots, 

 jDroduce fresh stems each season. 

 The Honeysuckle and the Bitter- 

 sweet, however, have perennial, 

 woody stems which increase in 

 thickness year by year, though the 

 latter does not twine very much, 

 and seems to take an inter- 

 mediate j)lace between the typical 

 twiners and the plants which 

 support themselves by merely in- 

 terlacing their stems with the 

 neighbouring plants or shrubs. 



Some twining stems are un- 

 able to form their spii-als round thick supports, and after making 

 some attempt to do so grow off at a tangent to seek some less 

 bulky prop. It has been observed, for instance, that the Hop 

 cannot grasp a pole that is more than four inches in diameter. 



In many cases, too, the spii-als of the twining stem increase in 

 diameter after they are fii'st formed, and can thus adapt themselves 



D 2 



STEM OF THE HOP, TWINING TO THE 

 RIGHT, 



