• DOI:10.2307/2804829
• Corpus ID: 23125349

Crataegus in the northeastern and central United States and adjacent Canada

@article{Palmer2008CrataegusIT,
  title={Crataegus in the northeastern and central United States and adjacent Canada},
  author={Ernest Jesse Palmer},
  journal={Brittonia},
  year={2008},
  volume={5},
  pages={471-490}
}

• E. Palmer
• Published 6 September 1946
• Biology
• Brittonia

In the preparation of a revised treatment of the genus Crcataegus in the northeastern United States and adjacent Canada, to be published soon, it has been found necessary to propose a new specific name to replace one invalidated by all earlier homonym and to change the status of a number of names from species to varieties or forms. And in treating the species under a broader concept than that of the original authors, many names are placed in synonymy. This more conservative treatment of the genus seems to be amply justified by extensive field studies, the examination of a very large amount of material in herbaria and in private collections, and by observations extending over a number of years of the hundreds of living plants in the Arnold Arboretum, most of which were grown from seeds taken from type trees or from type localities. As a result of these studies it is hoped that progress has been made in the understanding of many of the species and of their limits and relationships. But much more work must be done before anything like an adequate or final treatment of this difficult genus can be undertaken. At present many conclusions can only be tentative and based upon the best judgmenit of the'investigator. It must be recognized that there is no real uniformity of opinion among tax7 onomists on what constitutes a species or on how specific lines can be drawn between very similar and closely related plants or animals with variable and intergrading characters. And it would seem that there must always be a border-line or zone along which such agreement is impossible and within which there will continue to be differences of opinion. Under an evolutionary concept of nature it can readily be understood that various groups of organisms may stand at different stages in the process of differentiation, and that some forms may have become widely separated from their nearest allies while others are only beginning to diverge in different directions. It is, therefore, not at all surprising to find that authors and reviewers are often in disagreement as to whether certain plants should be regarded as distinct species, as varieties, or as forms, or should be merged with other forms in the broader concept of a single variable species. As everyone who has followed recent taxonomic literature knows, many botanical names have undergone changes in status, and it is not uncommon for authors to change their opinions in subsequent publications even about the validity or standing of their own proposed names. The logical significance of this situation is that classification into species in some sections at least of many of the larger plant genera is largely artificial and a matter of convenience. Crataegus, particularly in the parts of North America where it is most abulldantly developed, is a conspicuous example of a comparatively young and expanding genus in a state of instability and in process of evolution. Most of the species are smnall trees or arboreseent shrubs growing on the borders of woods, in glades, or on rocky hills, or springing up in naturally or artificially cleared areas where competition with other plants is not too keen. They are essentially "opportunists," and under primitive conditions when most of eastern North America was covered with a dense unbroken forest, the space available to them was very limited and there was little chance for the different species to come in contact with each other. Such conditions were not generally favorable for hybridization or for 471