It is not the object of this paper to supply specific information on the behaviour of pasture plants under various conditions of fertilization. I shall at,tempt to review some of the results obtained in work on various organisms, in the search for those principles which are fundiental to the phenomena forming the subject of this paper; fundamentals which, I admit,.may -q. not generally allow of a direct application in economic plant breeding, but which may ,lead the way to new ideas and. to 'new methods of procedure.
