HEDGE AND DITCH 157 



in which we live ? I know of six, besides Tamus. One is 

 to be found in the hazel-copse, another only in a single 

 corn-field, where it climbs up the wheat-stalks ; a third 

 overruns the hedge of a cottage-garden, the fourth over- 

 hangs the vicar's front door, and two more are to be found 

 in his kitchen-garden. (5) Look out for these, but do not 

 ravage either the gardens or the fields. Try to make out 

 the names of these twiners, and mark which follow the sun, 

 and which twine against the sun. Here is a stick of hazel 

 with a spiral groove running round it. What made the 

 groove ? Can you find more grooved sticks in the hazel - 

 copse ? The upper lip of the groove is thicker and more 

 prominent than the lower lip ; why ? (6) 



Hop. Watch the tip of a growing hop-shoot, and see 

 how it bends round and round its support, swaying in turn 

 towards every point of the compass. If the movement 

 were much more rapid, we might compare it to the weighted 

 string which the thoughtless schoolboy swings round his 

 head. As the string curls close about a lamp-post which 

 it happens to strike, so the hop-shoot, slowly swinging 

 in a circle, curls round any support which it can reach. 1 

 The climbing hop-stem not only becomes curled, but 

 twisted about its axis. If a shoot is marked not far from 

 its apex by a spot of paint, the twisting can be measured. 

 Darwin found that it is not constant for the same species 

 of twining plant. The mere act of twining produces one 

 twist for every circle completed, but if the climbing shoot 

 gets a good hold of its support, it may develop a greater 

 amount of twist than this. A long, free shoot, well-sup- 

 ported below, sometimes becomes extremely twisted by 

 its own twining. 



The observer who has a climbing hop under his eye 

 should mark on paper the movements of the apex. Note 

 the distance from the support with a pair of compasses, 

 and the varying angular position by the eye. Measure- 

 ments taken at intervals of a quarter of an hour will furnish 

 1 This happy illustration is borrowed from Darwin. 



