The extent to which the roots of many plants spread in the
soil is beautifully suited to the way in which the rain-water is
conducted down to the soil by the leaves. In some cases, as in
the Carrot and other plants with swollen roots, the leaves conduct
the rain water towards the centre of the plant, where it runs
down the stem to the tap-root. Such tap-roots have only small
side-roots. In other plants (see Mango tree, page 27) the water
is conducted from leaf to leaf towards the periphery of the tree
and there falls to the ground; and in these plants the ends of


THE ROOT 229


the side-roots will often be found just beneath the periphery of
their crowns. In the same measure as the crown of the tree
increases ik, width, its roots grow to have the full benefit of the
water falling from the leaves,

(c) oot-hairs.— Allow some seeds of maize or mustard to
germinate between sheets of moist blotting paper. Put each
plant into a phial filled with water fixing its stem in the neck of
the phial with a cotton stopper. Examine the roots and you


Vig. 211.—1. Root-hairs of the Mustard

seedling. 2. The same with particles of soil

clinging to the root-hairs. 3. Root-hairs

(R, 200 times enlarged), which are mere

outward prolongations of the cells forming
the epidermis (E).
