The vast body of information which the "Species Plantarum" contained was systematically arranged. All the different species in one genus were brought together. They were described, each under a number; and an adjective word, usually descriptive of some marked characteristic, was written in as a marginal index.
After Linnaeus's time botanists found that the genus name in combination with this marginal word made a convenient and exact means of designating the plant. Thus Linnaeus became the acknowledged originator of the binomial (two-name) system of nomenclature now in use in all sciences. It is a delightful coincidence that while Linnaeus was engaged on his great work, North America, that vast new field of botanical exploration, was being traversed by another Swedish scientist. Peter Kalm sent his specimens and his descriptive notes to Linnaeus, who described and named the new plants in his book. The specimens swelled the great herbarium at the University of Upsala.
Among trees unknown to science before are the Magnolia, named in honor of the great French botanist, Magnol. Robinia, the locust, honors another French botanist, Robin, and his son. Kalmia, the beautiful mountain laurel, immortalizes the name of the devoted explorer who discovered it.
Inevitably, duplication of names attended the work of the early scientists, isolated from each other, and far from libraries and herbaria. Any one discovering a plant he believed to be unknown to science published a description of it in some scientific journal. If some one else had described it at an earlier date, the fact became known in the course of time. The name earliest published is retained, and the later one is dropped to the rank of a synonym. If the name has been used before to describe some other species in the same genus, a new name must be supplied. In the "Cyclopedia of Horticulture" the sugar maple is written: "Acer saccharum, Marsh. (Acer saccharinum, Wang. Acer barbatum, Michx.)" This means that the earliest name given this tree by a botanist was that of Marshall. Wangheimer and Michaux are therefore thrown out; the names given by them are among the synonyms.
Our cork elm was until recently called "Ulmus racemosa, Thomas." The discovery that the name racemosa was given long ago to the cork elm of Europe discredited it for the American tree. Mr. Sargent substituted the name of the author, and it now stands "Ulmus Thomasi, Sarg." Occasionally a generic name is changed. The old generic name becomes the specific name. Box elder was formerly known as "Negundo aceroides, Mœnch." It is changed back to "Acer Negundo, Linn." On the other hand, the tan-bark oak, which is intermediate in character between oaks and chestnuts, has been taken by Professor Sargent in his Manual, 1905, out of the genus Quercus and set in a genus by itself. From "Quercus densiflora, Hook. and Arn." it is called "Pasania densiflora, Sarg.," the specific name being carried over to the new genus.
About one hundred thousand species of plants have been named by botanists. They believe that one half of the world's flora is covered. Trees are better known than less conspicuous plants. Fungi and bacteria are just coming into notice. Yet even among trees new species are constantly being described. Professor Sargent described 567 native species in his "Silva of North America," published 1892-1900. His Manual, 1905, contains 630. Both books exclude Mexico. The silva of the tropics contains many unknown trees, for there are still impenetrable tracts of forest.
The origin of local names of trees is interesting. History and romance, music and hard common sense are in these names—likewise much pure foolishness. The nearness to Mexico brought in the musical piñon and madroña in the southwest. Pecanier and bois d'arc came with many other French names with the Acadians to Louisiana. The Indians had many trees named, and we wisely kept hickory, wahoo, catalpa, persimmon, and a few others of them.
Woodsmen have generally chosen descriptive names which are based on fact and are helpful to learners. Botanists have done this, too. Bark gives the names to shagbark hickory, striped maple, and naked wood. The color names white birch, black locust, blue beech. Wood names red oak, yellow-wood, and white-heart hickory. The texture names rock elm, punk oak, and soft pine. The uses name post oak, canoe birch, and lodge-pole pine.
The tree habit is described by dwarf juniper and weeping spruce. The habitat by swamp maple, desert willow, and seaside alder. The range by California white oak and Georgia pine. Sap is characterized in sugar maple, sweet gum, balsam fir, and sweet birch. Twigs are indicated in clammy locust, cotton gum, winged elm. Leaf linings are referred to in silver maple, white poplar, and white basswood. Color of foliage, in gray pine, blue oak, and golden fir. Shape of leaves, in heart-leaved cucumber tree and ear-leaved umbrella. Resemblance of leaves to other species, in willow oak and parsley haw. The flowers of trees give names to tulip tree, silver-bell tree, and fringe tree. The fruit is described in big-cone pine, butternut, mossy-cup oak, and mock orange.
Many trees retain their classical names, which have become the generic botanical ones, as acacia, ailanthus, and viburnum. Others modify these slightly, as pine from Pinus, and poplar from Populus. The number of local names a species has depends upon the notice it attracts and the range it has. The loblolly pine, important as a lumber tree, extends along the coast from New Jersey to Texas. It has twenty-two nicknames.