by Nathaniel Lord Britton & Addison Brown

“ Critical field observations of plants in the wild state, supplemented by the cultivation side by side of species supposed to be distinct and by the lessons learned from experimental plant breeding, have developed the theory that many species, perhaps all, are composed of a greater or lesser number of races, differing from each other too little to cause them to be regarded as species, notwithstanding the fact that they may breed true from seed to such slight or trivial differentiations. ”

“ The critical study of plants, resulting in the present knowledge by botanists of many more genera and species than formerly, has made necessary more exact definition and determination of both genera and species by basing them on types, a method previously reached in zoology. ”

“ Its aim is to illustrate and describe every species, from the Ferns upward, recognized as distinct by botanists and growing wild within the area adopted, and to complete the work within such moderate limits of size and cost as shall make it accessible to the public generally, so that it may serve as an independent handbook of our Northern Flora and as a work of general reference, or as an adjunct and supplement to the manuals of systematic botany in current use.
To all botanical students, a complete illustrated manual is of the greatest service; always useful, often indispensable. ”

“ Dr. Asa Gray, in his Structural Botany, says (p. 348) :
"For each plant or group there can be only one valid name, and that always the most ancient, if it is tenable; consequently no new name should be given to an old plant or group, except for necessity."
This principle was applied to Zoology in the Stricklandian Code, adopted in 1842 as Rules of the British Association, and revised in 1860 and 1865 by a committee embracing the most eminent English authorities, such as Darwin, Henslow, Wallace, Clayton, Balfour, Huxley, Bentham and Hooker. ”

“ Scarcely one-quarter of the species illustrated in the present work have ever been figured before. That no such general work has been previously attempted is to be ascribed partly, perhaps, to the imperfect exploration of our territory, and the insufficiency of the collections to enable such a work to be made approximately complete; partly to the great number of species required to be figured and the consequent difficulty and cost of the undertaking, and partly to the lack of any apparent demand for such a work sufficient to warrant the expense of the enterprise. ”

“ In the present edition of Illustrated Flora, the view is taken that the races composing many species are often too numerous and too slightly characterized to be described so as to be recognized; many of them have been described as species and many more as varieties, and varieties of different degrees of differentation have been suggested. ”

“ The doubts and difficulties that are apt to attend the best written descriptions will often be instantly solved by figures addressed to the eye. The greatest stimulus, moreover, to observation and study, is a clear and intelligible guide ”

“ We here regard species alone as entitled to distinct botanical appelation; it has been suggested that races may be indicated numerically.
Other than the omission of descriptions of varieties, the general system of classification used in the first edition has been maintained in the second. A few new family groups and a number of genera have been separated or distinguished from their congeners. ”

“ The increased accumulations of material in our largest herbaria, the result of multiplied explorations, and the widely extended interest in the study of our native plants, seem now to justify the endeavor to supply a complete illustrated work adapted to general use. ”

“ It is therefore earnestly recommended that collections be carefully made, seeking to reduce as far as possible this more or less necessary incompleteness. Where satisfactory material can not be obtained, it will usually be found possible to reach the desired analysis by following out two or more lines of the key, and by comparing the results reached with the descriptions to determine the family, genus or species. The illustrations provide an almost indispensable aid in such cases. ”

“ The necessity for these rules of nomenclature arose from the great confusion that has existed through the many different botanical names for the same species or genera. Some species have had from 10 to 20 different names, and, worse still, different plants have often had the same name. For about 200,000 known species of plants there are not fewer than 700,000 recorded names. ”

“ Some have made the number of genera and families as few as possible. This results in associating under one name species or genera that present marked differences among themselves. The present tendency of expert opinion is to separate more freely into convenient natural groups, according to similarity of structure, habit, form or appearance. ”

“ Individuals are grouped, by similarity, into races; races into species; species into genera; genera into families; families into orders; orders into classes; classes into divisions or subkingdoms.
In addition to these main ranks, subordinate ones are sometimes employed, when closer grouping is desirable: thus a Class may be separated into Subclasses, as the Class Angiospermae into the Sublasses Monocotyledones and Dicotyledones; Families may be separated into Tribes, as in the treatment of Gramineae in the following pages; Genera are often separated into Subgenera; Species into Subspecies. ”

“ Many names, however, have been given to plants in honor of individuals, which, having nothing Latin about them except the terminal form, and the pronunciation given to them by botanical authors being diverse, are here accented like the names of the persons, so far as euphony will permit. This rule is followed because it is believed to agree with the prevailing usage among botanists in ordinary speech; because it is in accord with the commemorative object of such names, which ought not to be obscured by a forced and unnatural pronunciation ”

“ These principles are applied to the arrangement of the Subclasses Monocotyledones and Dicotyledones independently, the Monocotyledones being the simpler, as shown by the less degree of differentiation of their tissues, though their floral structure is not so very different nor their antiquity much greater, so far as present information goes. For these reasons it is considered that Typhaceae, Sparganiaceae and Naiadaceae are the simplest of the Monocotyledones, and Orchidaceae the most complex; Saururaceae the simplest family of Dicotyledones, and Compositae the most complex. ”

“ Inasmuch as evolution has not always been progressive, but some groups, on the contrary, have clearly been developed by degradation from more highly organized ones, and other groups have been produced by divergence along more than one line from the parent stock, no linear consecutive sequence can, at all points, truly represent the actual lines of descent. ”

“ By these facilities, not only will the study of our native plants be stimulated and widened among all classes, but the enjoyment, the knowledge and the scientific progress derivable from these studies will he proportionately increased. ”

“ It also seems to have been proved, by DeVries and others, that such differentiations may originate abruptly from seed, in a single generation, and remain constant for at least several generations thereafter if so isolated from their relatives as to prevent cross-pollination. ”

“ The text, founded upon a careful examination of living or herbarium specimens, has been chiefly prepared by him, with the assistance, however, of specialists in a few groups who have contributed the descriptions for certain families as stated in the footnotes. The figures also have been drawn by artists under his immediate supervision ”