Attention must be called to the indefiniteness of species and varieties of plums due chiefly to the extreme responsiveness of the plants to environment. On each side of the specific or varietal types there are wide ranges of variation. Since the relationships between types are often very close it is impossible to avoid some confusion in characters, for outliers of the types cannot but overlap. It might be well said that these outliers are connecting links and that groups so connected should be combined, but this would make specific division of the genus and varietal division of the species almost impossible. The groups must, therefore, be separated along more or less arbitrary lines. But such arbitrary separation does not prevent natural groups, if nature be broadly interpreted.
The chief value of the work in hand lies in its discussion of varieties. In the descriptions the aim has been to give as tersely as possible an idea of all of the characters of the plums described. With very few exceptions the technical descriptions of varieties are original and were made by those who have taken active part in the preparation of this book. Nearly all of the varieties having full descriptions grow on the Station grounds but whenever possible specimens of each variety from different localities have been compared with those growing here.
A special effort has been made to give as exactly as possible the regions in which the species and varieties of plums grow. Such an effort is made under the belief that this knowledge is of great value in the study of the factors which govern the distribution of wild and domesticated plants. If the boundaries of the regions in which a few scores of varieties of the several fruits grow can be accurately established valuable generalizations can be drawn regarding life zones and plant distribution.
The reader should know what considerations have governed the selection of varieties for color-plates and full descriptions. These are: (1) The known value of the variety for the commercial or amateur grower. (2) The probable value of new varieties. (3) To furnish data for the plum-breeder; to show combinations of species or varieties, or new characters, or the range in variation. (4) Some sorts have been described because of historical value—to better show what the trend of plum evolution has been. (5) To indicate the relationships of species and varieties. The varieties are divided into three groups according to their importance as gauged from the standpoints given above.
In botanical nomenclature the code adopted by the American botanists in Philadelphia in 1904 and modified by the International Botanical Congress at Vienna in 1905, has been used. For horticultural names, lacking a better code, the revised rules of the American Pomological Society have been followed, though in a few cases we have not seen fit to follow the rules of this society, as the changes required by their strict observance would have brought much confusion. Only those who have to work with a great number of varieties of fruit can know the chaotic conditions of our pomological nomenclature. One of the aims of the work in hand is to set straight in some degree the great confusion in plum names.
All synonyms of varieties have been given so far as they could be determined but it did not seem worth while to give all of the references to be found even in standard plum literature. Fewer of these are listed for the leading varieties than in the books on apples or grapes which have preceded, only such being given as have been found of use by the writers or thought of possible use to future plum students. On the other hand some references have been given for all varieties, a task not attempted in The Grapes of New York.
As in the preceding books the color-plates have been given much attention. Work and expense have not been spared to make the plates the best possible with the present knowledge of color-printing. Yet the illustrations are not exact reproductions. The colors are, at best, only approximations; for it is impossible by mechanical processes to reproduce Nature’s delicate tints and shades. The camera does not take colors as the human eye sees them; and the maker of the copper plate can not quite reproduce all that the camera has taken. The colors then depend on the judgment of the printer, who by selecting and mingling colored inks, reproduces as nearly as his materials permit, the shades in his eye and mind; but no two persons see exactly the same colors in any object; so his conception may differ much from that of the horticulturist or artist who saw the original plum, as do theirs from each other. Still it is hoped that the color-plates will be of great service in illustrating the text. All of the plums from which the plates were made came from the Station grounds; the illustrations, with a few exceptions which are noted, are of life size, as grown under the conditions existing at this place, and as far as possible all are from specimens of average size and color.
Acknowledgments are due in particular to the plum-growers of New York who have furnished much information for The Plums of New York; to numerous institutions in all parts of the United States who have loaned botanical specimens; to Professor Charles Sprague Sargent for advice, information and the use of the Arnold Arboretum library and herbarium; to W. F. Wight of the United States Department of Agriculture, who has given most valuable assistance in describing the species of plums and in giving their range; to the Station Editor, F. H. Hall, who has had charge of the proof-reading; to Zeese-Wilkinson and Company, New York City, for their care and skill in making the color-plates; and to the J. B. Lyon Company, Albany, New York, for their careful work in the mechanical construction of the book.
U. P. HEDRICK,
Horticulturist, New York Agricultural Experiment Station.