Climbing Plants rely, 
first-formed joints, or ‘‘ internodes,” of the stem are 
straight, and stand erect and still. ‘‘But the next 
formed,” says Darwin, ‘‘whilst very young, may 
be seen to bend to one side, and to travel slowly 
around toward all points of the compass, moving 
like the hands of a watch, with the sun.” The 
movement very soon acquires its full ordinary ve- 
locity, and it continues as long as the plant con- 
tinues to grow; but each separate internode, as 
it becomes old, ceases to move. The internodes 
travel slowly when they are very young, and ac- 
celerate their speed as they approach maturity. 
So the tender tip and the lower and older part 
of the spray are moving in the same direction, 
but at varying rates; and this difference some- 
times gives a serpentine twist to the shoots of 
vigorous twiners. The ends of many vine-sprays 
are bent over so as to form hooks, which are of 
great assistance to the plants in their efforts to rise 
in the world. For not only does the terminal 
hook lay hold of any support within reach, but it 
causes the tip of the shoot to embrace this sup- 
port much more closely than it could otherwise do, 
and thus may prevent the stem from being blown 
aside in windy weather. It is very noticeable in the 
young sprays of the Virginia creeper (see Fig. 67). 
