not be poisonous to other plants of a different kind.  Thus, by rotation of crops, good crops could be grown indefinitely on the same land without the addition of plant food.  He said that the soil water alone dissolved plenty of plant food from all soils for the production of good crops, and that the supply of plant food will be permanently maintained, because the plant food contained in the subsoil far below where the roots go is being brought to the surface by the rise of the capillary moisture, and that there is in fact a steady tendency toward an accumulation 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 is any particular connection between the growing of wheat seedlings in small pots or bottles for a few twenty-day periods and the growing of crops in soils during successive seasons.  No, I don’t take any stock in their theories.  I think they are watered, or perhaps I should say hydrated, in deference to science.  But I would like to know about this question of plant food coming up from below.  That would be a happy solution of the fertilizer problem.”