58 THE BOOK OF NATURE STUDY 



hedge it is often found twisting round a grass, then the tip of 

 the stem may hang in the air for a while, until it catches hold of 

 some other plant, and both together will climb up the Hawthorn, 

 of which the hedge is composed, until they reach the top, where 

 they can get the light. The Black Bryony must not be confused 

 with the White Bryony, which is also a climbing plant. This 

 latter has tendrils and very different leaves from the former. 

 The Hop and the Convolvulus are instances of plants with twining 

 stems, each in a different direction from the other. Scarlet 

 Runners or Kidney Beans may be observed in any kitchen garden. 

 In order to see how stems twine, the following easy experiment 

 may be tried. Plant some Kidney Beans in a pot, and when 

 the shoot has grown to about a foot in length, tie the stem 

 to a stick 8 inches high. This will leave some 4 inches of 

 the stem hanging over. This will revolve. Place a sheet of 

 paper underneath the pot, make a dot to represent the tip of 

 the stem at regular intervals ; in this way a tracing of the move- 

 ment of the stem will be obtained. That plants climb by their 

 leaves has already been discussed. 



The effect of light on the growth of a stem is varied. 



1. If exposed to light on all sides, the internodes are shorter 

 than they would be if the plant has been deprived of light. A 

 plant growing in a hedge should be compared with the same 

 species growing in the open. 



2. Stems, not naturally climbing, sometimes are very much bent 

 and curved in their struggle to reach the light. On 2gth July 

 a species of Campanula growing in a high hedge on the sheltered 

 side of the road was gathered. The stem had no less than 

 four bends and curves, owing to the attempts it had made 

 to reach the light. It was much entangled with other plants 

 growing round one, then another, until its purple blossoms stood 

 out to the light. Ferns kept in a room often bend towards the 

 window. 



CONCLUSION. The adaptation of structure to function is very 

 striking in both stem and leaf. The best way of realising this 

 is to observe plants in their natural habitats as far as possible ; 

 this can easily be done by those living in the country. They can 



