kingdom"; sugar cane—the "honey without bees" of the an-
cients; and meadow grasses: bluegrass, brome grass, and
rye grass. Man grows copses of the giant grass—bamboo.
Many scientists are convinced that the vast cohort of
the Legume or Pea family (otherwise known as the Papilio-
naceae) come second only to grasses in their importance to
man. It is sufficient to mention peas and beans; soya,, which
is well known in our country and in China, is food for tens
of millions of people; and lentils, of which a Biblical hero
was so fond that he sold his birthright for a mess of this pot-
tage—all these are legumes. Everybody is also familiar
with ground nuts—arachis. From legumes medicines are
obtained: from liquorice and from the Peruvian tree (the
famous balsam). The best meadow grasses are also legumes:
alfalfa, clover, melilot, vetch, vigna and esparto grass.
These are wonderful grasses: they renew and enrich
the soil.
No organism, animal or plant, will grow or develop if
there is 110 nitrogen in its food> for no living body can be
built without nitrogen. Without nitrogen there can be no
protein substances, the foundation of life.
Everybody knows what high value is attached to nitrogenous
fertilizer, which has to be put into soil that is poor in nitrogen.
But how can that be? How can a plant suffer from a lack
of nitrogen? There may be little in the soil, but over the
soil there is a vast ocean of air, nearly four fifths of which
consists of nitrogen. The leaves and stems simply bathe in it!
But the whole point is that the plant cannot take the
nitrogen from the air. The elusive nitrogen passes through
the pores of the leaves, slips past the hungry tissue, even
penetrates it and slips out again and leaves no trace. The
plant can take it only when it ceases to be a gas, when it
forms nitrates, when water dissolves it and the roots ab-
37,