THE IVY 



into a double spiral, one part in one direction and the other 

 in the opposite way, with a flat piece between them. 



One might be disposed to think no more about these 

 double coils ; but here comes in one of the curious, inex- 

 plicable coincidences which happen so often in plant life. Such 

 a coil is much stronger than a straight bit of wire or string 

 would be, because if pulled out it yields and is springy. 

 That of course makes it less probable that the tendril will 

 be broken. Attached by a series of wiry springs, the plant 

 yields and sways to the wind, and it is not likely that it will 

 be torn away. Besides this, the coiling of the tendril pulls 

 the stem closer to its support, which is also a great ad- 

 vantage. 



Certain Virginian Creepers and Vines behave in quite a 

 different manner. The tendrils grow away from the light 

 and so seek the shadow of the leaves. They are also divided 

 into little branches. At the tip of each little branch is a 

 small knob ; if this should touch the wall or the trunk of a 

 tree, etc., it immediately secretes a drop of cement and glues 

 itself firmly to the wall. There is a curious difference in 

 different sorts of Ampelopsis in this respect. There is no 

 adhesive pad in one of them {Ampelopsis hederacea) until it 

 touches, whilst A, Veitchii has them more or less ready for 

 gluing before they touch (though they become much 

 larger and better developed as soon as they rub against the 

 waliy 



One of the most interesting of our common climbers, "that 

 rare old plant the Ivy green," has not yet been mentioned. 

 It is exceedingly decorative on walls, especially on ruins and 

 on old tree-trunks in winter time, where its dark, brilliant 

 green is most effective. 



1 Henslow, Origin of Plant Structures^ p. 223. 

 323 



