Plant Associations on Land

Abstract

The earth is populated by an innumerable host of plants and animals, tio two of which, it is generally agreed, are exactly alike. Happily they do have such likenesses as enable us to classify them into less and more inclusive categories. The objects are discovered by us. Their likenesses are discovered. The degrees of likeness and difference are discovered. And on these discoveries our categories are based. The names of the categories we invent. The evaluation of the likenesses and differences is highly subjective, as indeed the word value implies. If there is any test of such values, it must be the discovery of the usefulness of the categories for purposes of thought for the using and the increase of knowledge. By this test of usefulness for purposes of thought every system of classification has its values. It is valuable to its users. Some other scheme might be even more valuable. Thus schemes are tried and gain more or less wide acceptance. Perhaps for a long time one system prevails to the. exclusion of all others, as was true of the binomial system of nomenclature. At least in the testing stage one's sense of values depends upon experience and training. With those who break new paths in the realm of description and classification experience is the thing that counts. Thus a knowledge of the field in which a genius has worked, along with his historic background, gives an understanding or explanation of the viewpoints of the genius. Of the many workers who have studied natural vegetation we may single out a few who seem to have had especial influence upon contemporary thought, description and classification. It might be well to speak rather of schools than of persons. Thus we should consider the Ziirich-Montpellier School, the Scandinavian School, the Danish School, the Russian School, the Chicago School, and the Nebraska School.