12 
HOW PLANTS CLIMB. 
10. Root-Climbers. These cregp up the face of rocks or walls, or the trunks of 
trees, their stems, as they grow, pressing against the support and adhering to it by 
means of numerous rootlets which they throw out : the end of these rootlets com- 
monly flattens out or expands into a small disk or holdfast which adheres to the 
wall or bark, etc. Ivy, that is, true or “English” Ivy, is a good example of this. 
See the vignette title-page, left-hand side. Our Poison Ivy and the Trumpet 
Creeper climb in the same way. There is, perhaps, no more effectual mode of 
climbing when bare walls or large trunks are the support. In other cases 
11. Twiners, i. e. Twining Plants, have an obvious advantage. To twine spi- 
rally round some supporting body is a common mode of climbing. This is 
> m done by a 
Jr movement 
of the stem 
itself, not 
less re- 
markable in reality than that of the leaflets of the Desmo- 
dium gyrans, just described, and indeed of similar nature. 
The Hop and some Honeysuckles twine with the sun. 
Morning Glory, and all the Bindweeds of the Convolvulus 
Family, Beans, and indeed most of the common twiners, 
turn against the sun, that is, from the left to the right 
hand of the observer. 
12. When a twining stem overtops its support, the 
lengthening shoot is seen thrown over to one side, and 
usually outstretched, as in Fig. 3. One might suppose it 
had fallen over by its weight ; but it is not generally so. 
If turned over, say to the north, when first observed, it will 
probably be found reclining to the south an hour or so 
later, and an hour later again turned northward. That is, 
the end of the stem is sweeping round in a circle continu- 
ally, like the hand of a clock. It keeps on growing as it 
rig. 3. Morning Glory, twining, revolves; but the revolving has nothing to do with the 
growth, and, indeed, is often so rapid that several complete sweeps may be made 
before any increase in length could be observed. The time of revolving varies in 
different species. It also depends upon the weather, being slow or imperceptible 
