a root in
loving darkness, while yet it has enough consciousness of better things to
grow towards, or near, the light. In one family it is even fragrant where
the flower is not, and a simple houseleek is called 'rhodiola rosea,'
because its root-stock has the scent of a rose.

16. There is one very unusual condition of the root-stock which has become
of much importance in economy, though it is of little in botany; the
forming, namely, of knots at the ends of the branches of the underground
stem, where the new roots are to be thrown out. Of these knots, or
'tubers,' (swollen things,) one kind, belonging to {38} the tobacco tribe,
has been singularly harmful, together with its pungent relative, to a
neighbouring country of ours, which perhaps may reach a higher destiny than
any of its friends can conceive for it, if it can ever succeed in living
without either the potato, or the pipe.

17. Being prepared now to find among plants many things which are like
roots, yet are not; you may simplify and make fast your true idea of a root
as a fibre or group of fibres, which fixes, animates, and partly feeds the
leaf. Then practically, as you examine plants in detail, ask first
respecting them: What kind of root have they? Is it large or small in
proportion to their bulk, and why is it so? What soil does it like, and
what properties does it acquire from it? The endeavour to answer these
questions will soon lead you to a rational inquiry into the plant's
history. You will first ascertain what rock or earth it delights in, and
what climate and circumstances; then you will see how its root is fitted to
sustain it mechanically under given pressures and violences, and to find
for it the necessary sustenance under given difficulties of famine or
drought. Lastly you will consider what chemical actions appear to be going
on in the root, or its store; what processes there are, and elements, which
give pungency to the radish, flavour to the onion, or sweetness to the
liquorice; and of what service each root may be made capable under
cultivation, and by proper subsequent treatment, either to animals or men.

18. I shall not attempt to do any of this for you; I {39} assume, in giving
this advice, that you wish to pursue the science of botany as your chief
study; I have only broken moments for it, snatched from my chief
occupations, and I have done nothing myself of all this I tell you to do.
But so far as you can work in this manner, even if