Trees of the Northern United States. A. C. Apgar
been rewritten. That work includes every species, native and naturalized, of the region covered by this book, and the names as given in that edition have been used in all cases.
Scientific names are marked so as to indicate the pronunciation. The vowel of the accented syllable is marked by the grave accent (`) if long, and by the acute (´) if short.
In the preparation of this book the author has received much valuable aid. His thanks are especially due to the authorities of the Arnold Arboretum, Boston, Massachusetts, and of the Missouri Botanical Garden, St. Louis, for information in regard to the hardiness of species; to Mr. John H. Redfield, of the Botanical Department of the Philadelphia Academy of Natural Sciences, for books, specimens from which to make illustrations, etc.; and to Dr. A. C. Stokes, of Trenton, New Jersey, for assistance in many ways, but especially for the accurate manner in which he has inked the illustrations from the author's pencil-drawings.
The author also wishes to acknowledge the help received from many nurserymen in gathering specimens for illustration and in giving information of great value. Among these, special thanks are due to Mr. Samuel C. Moon, of Morrisville Nurseries, who placed his large collection of living specimens at the author's disposal, and in many other ways gave him much intelligent aid.
TREES.
PART I.
THE ESSENTIAL ORGANS, AND THE TERMS NEEDED FOR THEIR DESCRIPTION.
Chapter I.
Roots.
Though but little study of the roots of trees is practicable, some knowledge of their forms, varieties, and parts is important.
The great office of the roots of all plants is the taking in of food from the soil. Thick or fleshy roots, such as the radish, are stocks of food prepared for the future growth of the plant, or for the production of flowers and fruit. The thick roots of trees are designed mainly for their secure fastening in the soil. The real mouths by which the food is taken in are the minute tips of the hair-like roots found over the surface of the smaller branches. As trees especially need a strong support, they all have either a tap-root—one large root extending from the lower end of the trunk deep down into the ground; or multiple roots—a number of large roots mainly extending outward from the base of the trunk.
Trees with large tap-roots are very hard to transplant, and cannot with safety be transferred after they have attained any real size. The Hickories and Oaks belong to this class.
Trees having multiple roots are readily transplanted, even when large. The Maples and Elms are of this class.
Roots that grow from the root-end of the embryo of the seed are called primary roots; those growing from slips or from stems anywhere are secondary roots.
Some trees grow luxuriantly with only secondary roots; such trees can readily be raised from stems placed in the ground. The Willows and Poplars are good examples of this group. Other trees need all the strength that primary roots can give them; these have to be raised from seed. Peach-trees are specially good examples, but practically most trees are best raised from seed.
A few trees can be easily raised from root-cuttings or from suckers which grow up from roots. The Ailanthus, or "Tree of Heaven," is best raised in this way. Of this tree there are three kinds, two of which have disagreeable odors when in bloom, but the other is nearly odorless. By using the roots or the suckers of the third kind, only those which would be pleasant to have in a neighborhood would be obtained. One of the large cities of the United States has in its streets thousands of the most displeasing of these varieties and but few of the right sort, all because the nurseryman who originally supplied the city used root-cuttings from the disagreeable kind.
If such trees were raised from the seed, only about one third would be desirable, and their character could be determined only when they had reached such a size as to produce fruit, when it would be too late to transplant them. Fruit-trees, when raised from the seed, have to be grafted with the desired variety in order to secure good fruit when they reach the bearing age.
Chapter II.
Stems and Branches.
The stem is the distinguishing characteristic of trees, separating them from all other groups of plants. Although in the region covered by this book the trees include all the very large plants, size alone does not make a tree.
A plant with a single trunk of woody structure that does not branch for some distance above the ground, is called a tree. Woody plants that branch directly above the soil, even though they grow to the height of twenty feet or more, are called shrubs, or, in popular language, bushes. Many plants which have a tendency to grow into the form of shrubs may, by pruning, be forced to grow tree-like; some that are shrubs in the northern States are trees further south.
All the trees that grow wild, or can be cultivated out of doors, in the northern States belong to one class, the stems having a separable bark on the outside, a minute stem of pith in the center, and, between these, wood in annual layers. Such a stem is called exogenous (outside-growing), because a new layer forms on the outside of the wood each year.
Fig. 1.
Another kind of tree-stem is found abundantly in the tropics; one, the Palmetto, grows from South Carolina to Florida. While in our region there are no trees of this character, there are plants having this kind of stem, the best illustration being the corn-stalk. In this case there is no separable bark, and the woody substance is in threads within the pithy material. In the corn-stalk the woody threads are not very numerous, and the pith is very abundant; in most of the tropical trees belonging to this group the threads of wood are so numerous as to make the material very durable and fit for furniture. A stem of this kind is called endogenous (inside-growing). Fig. 1 represents a longitudinal and a cross section of an exogenous stem, and Fig. 2 of an endogenous one.
Fig. 2.
Since all the stems with which we have to deal are exogens, a particular description of that class will here be given. Fig. 1 shows the appearance of a section of an Ash stem six years old. The central portion, which is about as thick as wrapping-twine, is the pith; from this outward toward the bark can be seen the six annual layers of the wood; and then comes the bark, consisting of two portions. First there is an inside layer of greenish material, the fresh-growing portion, and lastly the outer or dead matter. This outer portion must crack open, peel off, or in some way give a chance for the constant growth of the trunk. The different kinds of trees are readily known by the appearance of the bark of the trunk, due to the many varieties of surface caused by the allowance for growth. None of the characteristics of trees afford a better opportunity for careful observation and study than the outer bark.
The Birches have bark that peels off in thin horizontal layers—the color, thinness, and toughness differing in the different species; the Ashes have bark which opens in many irregular, netted cracks moderately near each other; the bark of the Chestnut opens in large longitudinal cracks quite distant from one another. The color of the bark and the character of the scales are quite