ments, and discard the popular belief that inorganic nutrients in
soils are transmitted from soils to plants, and therein contained for
the express purpose of satisfying the need of animals and humans[23].

The plant has only one purpose to perform which is to grow and to
reproduce itself, and such is the case with all other forms of life.

Plants contain very often inorganic elements in a form in which they
cannot be utilized. It is therefore quite easy to mistake their presence
either as a toxicity symptom or as a high requirement, when as a matter
of fact these elements are present due to conditions unfavorable to
metabolism, and they remained in bark and leaves as end products, in an
inert form. Rather than being transmitted from soils to plant, their
functions may consist of the formation of enzymes, proteins, hormones,
chlorophyll, antibodies, vitamins, in carbon assimilation. When they
have served such purposes they are not likely to be present in plants in
anything like the amounts or forms as present in soils. They may come
into question as catalysts or bio-catalysts, as sources of energy for
microorganism, from which their optimum effects have been secured when
they are not transmitted at all, causing changes, but remaining
themselves unchanged. They are essential in the sense that the elements
composing soils, sea, atmosphere are constantly energized, changed and
used over and over again to create plant, animal and human life. In this
cycle nothing is lost, only changed from old to new generations.

Summary

Soil factors for tree growth are physical, chemical and biological. To
control the organisms of soils and plants is probably the most difficult
problem in microbiology. It is not wise to alternate neglect with
feverish attention when blights or other pests become epidemic or
threatening. They may be of a nutritional, preventable rather than
curable nature. Pathology and tree nutrition may as well become a
constant part of your activities.

References to the Literature

1. BEESON, K. C. The Mineral Composition of Crops U.S.D.A. Bulletin No.
369. March, 1941

2. FEARON, W. R. A Classification of the Biological Elements Sci. Proc.
Royal Dublin Soc. Vol. 20 No. 35. February, 1933

3. WISCHHUSEN, J. F. Minerals in Agricultural and in Animal Husbandry
Manganese Research & Development Foundation Cleveland 10, Ohio

4. RODALE, J. I. The Organic Forest--Editorial Organic Gardening,
Emmaus, Pa. April,