of plant food in the surface soil. He said that it is never
necessary to apply fertilizing material to any soil for the purpose
of increasing the supply of plant food in that soil. He admitted
that applications of fertilizers sometimes produce increased crop
yields, but that the effect was due to the power of the fertilizer
to destroy the toxic substances excreted by the plants, and this is
really the principal effect of potash, phosphates, and nitrates, and
also of farm manure and green manures. Humus, he said, is one of the
very best substances for destroying these toxic excrete although
they had some other things which were as good or better than any
sore of fertilizing materials. He mentioned especially a substance
called pyrogallol, which cost $2.00 a pound, and of course it could
not be applied on a large scale; but it was as good a fertilizer as
anything, although it contains nothing but carbon, oxygen, and
hydrogen, which, as you explained to me when you were here before,
the plants secure in abundance from air and water. This information
had been secured in the laboratories at Washington by growing wheat
seedlings in water culture for twenty-day periods."

"I have already heard something of those theories," said Percy, "but
I shall be glad to have you tell me more about them. As I understand
them, we need only to rotate and cultivate and our lands should
always continue to produce bountiful crops. Is that correct?"

"I understand that is the theory," replied Mr. West, "but I know it
is not correct for my grandfather used to grow two or three times as
much wheat per acre as I can grow, and I rotate much more than he
did. In fact I can grow only ten to fifteen bushels of wheat per
acre once in ten years, whereas he grew from twenty-five to forty
bushels per acre in a five-year rotation; and I don't see that there