56 ESSENTIALS OF BOTANY 
the cinquefoil, the white clover, the dandelion, the spurges, 
the knot-grass, and hundreds of other kinds of plants have 
found safety in hugging the ground. 
73. Climbing and Twining Stems.' — Since it is essential 
to the health and rapid growth of most plants that they 
should have free access to the sun and air, it is not strange 
that many should resort to special 
devices for lifting themselves 
above their neighbors. In trop-~ 
ical forests, where the darkness of 
the shade anywhere beneath the 
tree-tops is so great that few 
wi? flowering plants can thrive in 
i it, the climbing plants, or lianas, 
often run like great cables for 
hundreds of feet before they can 
emerge into the sunshine above, 
and share the light with the trees 
which support them. In temper- 
ate climates no such remarkable 
climbers are found, but many 
plants raise themselves for con- 
siderable distances. The princi- 
pal means to which they resort 
for this purpose are: 
(1) Producing roots at many points along the stem above 
ground and climbing on suitable objects by means of these, 
as in the English ivy (Fig. 13). 
(2) Laying hold of objects by means of tendrils or twin- 
ing branches or leaf-stalks (Figs. 28, 29). 
(8) Twining about any slender upright support (Fig. 30). 
f fi \ 
| a i 
Fie. 28. Coiling of a Tendril 
of Bryony. 
1 See Kerner and Oliver’s Natural History of Plants, Vol. 1, p. 669. 
