Abstract
IN the Transactions of the British Mycological Society (vol. vi., part ii., September, 1919) Mr. W. B. Brierley protests against the practice of mycologists in describing as species the forms which are presented to them in Nature or as pathological growths, especially on cultivated plants. The description of new fungal species is based on the assumptions that the distinguishing characters are of a morphological nature, and that the essential specific characters are constant and hereditary and may be determined in one specimen of one generation. But the laboratory and field experience of the experimentalist shows that under changes in the environment the whole structure and facies of the organism may be transformed, while under identical conditions there is considerable evidence that the morphological variation of a particular fungus is definite and constant. The so-called species of the mycologist is comparable with the “ecad” of the ecologist, and is the resultant of the organism and its environment. “Ecads” indistinguishable from each other may be produced from two distinct organisms interacting with one and the same environment, or with two different environments. Two precisely similar fungi growing on a potato and a decaying tree-stump respectively may really be different species, though the systematic mycologist would consider them identical. The true organism is a physiological equilibration, a metabolic entity, the interaction of which with the environment results in the growth-form or “ecad.” It follows that the morphological species concept must be given up in favour of the physiological species concept. The only exact method of determining species is by means of quantitative data derived from cultural treatment under standardised physico-chemical conditions, for this method alone reveals the physiological condition of the organism. The author suggests that even the apparently stable forms of the higher fungi, Agarics, Polypores, etc., are merely “ecads,” and that two precisely similar morphological entities of, for instance, Agaricus melleus may conceal totally different physiological constitutions which under other conditions of growth would diverge characteristically.
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The Species Concept among Fungi . Nature 104, 708 (1920). https://doi.org/10.1038/104708a0
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DOI: https://doi.org/10.1038/104708a0