y identical. But
soil differs greatly from place to place. Here it's black; there it's
yellow; here it's rich loam; there it's boggy mould or sandy gravel.
And some soils are better adapted to growing certain plants than
others. Rich lowlands and oolites suit the cereals; red marl produces
wonderful grazing grass; bare uplands are best for gorse and heather.
Hence everything favours for the practical man the mistaken idea that
plants and trees grow mainly out of the soil. His own eyes tell him so;
he sees them growing, he sees the visible result undeniable before his
face; while the real act of feeding off the carbon in the air is wholly
unknown to him, being realizable only by the aid of the microscope,
aided by the most delicate and difficult chemical analysis.

Nevertheless French chemists have amply proved by actual experiment
that plants can grow and produce excellent results without any aid from
the soil at all. You have only to suspend the seeds freely in the air
by a string, and supply the rootlets of the sprouting seedlings with a
little water, containing in solution small quantities of manure-stuffs,
and the plants will grow as well as on their native heath, or even
better. Indeed, nature has tried the same experiment on a larger scale
in many cases, as with the cliff-side plants that root themselves in
the naked clefts of granite rocks; the tropical orchids that fasten
lightly on the bark of huge forest trees; and the mosses that spread
even over the bare face of hard brick walls, with scarcely a chink or
cranny in which to fasten their minute rootlets. The insect-eating
plants are also interesting examples in their way of the curious means
which nature takes for keeping up the manure supply under trying
circumstances. These uncanny things are all denizens of loose, peaty
soil, where they can root themselves sufficiently for purposes of
foothold and drink, but where the water rapidly washes away all animal
matter. Under such conditions the cunning sundews and the ruthless
pitcher-plants set deceptive honey traps for unsuspecting insects,
which they catch and kill, absorbing and using up the protoplasmic
contents of their bodies, by way of manure, to supply their quota of
nitrogenous material.

It is the literal fact, then, that plants really eat and live off
carbon, just as truly as sheep eat grass or lions eat antelopes; and
that the green leaves are the mouths and stomachs with which they eat
and digest i