V Arrangement By Natural Affinities (Botanical). This system is the one adopted throughout this work. It is of all others the most scientific by which plants may be studied, and, as the official portions of vegetable drugs are but parts of the whole, it seems only natural that the parental source should furnish the basis of classification for these medicinal parts. Everyone knows that there are greater similarities and dissimilarities between some plants than between others, and that this likewise applies to animals. Scientists, taking advantage of this fact, have for several centuries been trying to form groups of plants, each to contain only those possessing, in common, certain marks of resemblance, and so naming the same, when possible, to typify the strongest characteristic. Early botanists were content with one point of agreement, but they differed even as to what plant-organ, above all others, should be accepted to furnish this point, hence the basis of a system. Caevsalpinus (1519-1603) selected the fruit, the globular furnishing one class, the flat another, etc. Tournefort (1656-1708) took the flower, restricting himself to the modification and arrangement of the corolla, the cup-shaped being one class, the bell-shaped another, etc. Linnaeus (1707-1778) went a step further, and founded classes and orders upon the position, number, and relative lengths of the stamens and pistils, giving us the Linnsean, artificial, or sexual system of plants. This worked very well until cultivation, climatic differences, etc., changed the number of stamens and pistils. So far, no one had taken into consideration the plant's entirety. It is to John Ray (1628-1705), often called the "father of English natural history," that we owe the conception of a broader and more natural system; but it was Jussieu (1748-1836) who, embodying the grand features of both Ray and Tournefort, laid the permanent foundation of the true natural system which, somewhat modified, has come down to us. The very foundation of this system necessitates the faithful consideration of the similarities in form, structure, growth, habits, functions, thereby involving the idea of "affinity in essential organs." These understood, we may arrange the entire vegetable kingdom into allied groups of a scaling grade, dependent upon their whole make-up, thus placing each family (natural order) genus, and species next to those it most resembles in all respects.
Families or Natural Orders. - Of these there are about 280; they are the broader groups, and each comprises plants resembling one another in some strong particular, which applies to them generally as a class; this characteristic usually is taken from one of the reproductive organs (flowers, fruit, seed), and is so striking as to be noticeable by the inexperienced: Leguminosae (fruit in legumes), Umbelliferae (flowers in umbels), Compositae (flowers compound), Labiatae (corolla 2-lipped), Cupuliferae (fruit in cupule), Guttiferae (juice exudes in drops), Coniferae (fruit in cones), Cruciferae (petals arranged like a Maltese cross), etc.
Genus, Genera. - Of these there are about 10,000; they are more restricted groups, and go to compose the families or natural orders. This name corresponds to the family, surname, or last name of persons, Brown, Jones, Smith; it is a noun, and, like the family (ordinal) name, begins with a capital. Genera also are grouped according to some certain but more restricted characteristic taken from the reproductive organs; hence a genus is a collection of species resembling one another in the structure and general characters of the organs of reproduction, or in reproductive processes, methods of fructification, pollination, etc. Plants of the same genus are expected to be on the same numerical plan, and to have flowers, constituents, and medicinal properties somewhat similar.
Species, Species. - Of these there are about 200,000; they are the most restricted permanent groups and make up the various genera. This name corresponds to the baptismal or first name of persons, James, John, William; it is usually an adjective agreeing in case and gender with generic name, and, as such, should begin with a small letter. These are grouped according to some certain but still more restricted characteristics taken usually from the vegetative organs (root, stem, leaves), as color, proportion, shape, surface, duration, division, etc.; hence, species is a succession of individuals which reproduces and perpetuates itself. The last two names, generic and specific, when taken together, constitute the plant's name - i. e., botanical source or origin - and consequently every plant (and animal) thus always is designated.
There are two scientific methods (with their many modifications) of arranging each family (natural order), genus, and species toward its nearest neighbor. Thus we may follow Jussieu's sequence, beginning with the cellular, flowerless, or lowest plant-life (Algae), advancing to those of vascular structure, with apologetic, imperfect, or incomplete floral parts, always having each to follow in the ascending scale, finally reaching those producing as then understood the most perfect, complete, and typical flowers (Ranunculaceae). De Candolle (1778-1841) greatly innovated this system, but chiefly in reversing the arrangement, placing the most highly organized plants, or flower producers, first in order, and each lower one in a descending succession. This would seem the most unnatural, as the order of development in nature surely suggests evolution from forms more simple to those more complex, and not the converse. In spite of this, however, it has universally been accepted for the past half-century, being strongly indorsed and followed by many of the world's greatest botanists, including Bentley, Trimen, Hanbury, Gray, Balfour, Bentham, Hooker, etc.; and is enunciated best by Bentham and Hooker in their Genera Plantarum.
The other plan, being the most rational, has continued always to have supporters, and during the past two decades has been studied systematically and thoroughly, especially in Germany, with more than ordinary zeal and results. Such scholars as Eichler, Engler, Prantl, Thome, Potonie, Richter, Fluckiger, Kohler, Stasburger, Schenck, Schimper, etc., have instituted many changes, and, although beginning with the most primitive plant-life and ending with those bearing most complex flowers (Compositae), have succeeded in evolving the system in a form much more consistent and in harmony with modern scientific thought and general plant-nature. As such, it is enunciated best by Engler and Prantl in their Die Naturlichen Pflanzenfamilien, and by Engler in his Syllabus der Pflanzenjamilien, and as this is the sequence that necessarily must come into future favor, it has been thought wise, in the main, to adhere to it in this work, giving thereto the following synopsis: