same order that is used in the detailed descriptions of species being maintained in the present discussion. A few drawings will also be added to make clear certain points and to show comparative forms.

NAME.—Every tree has one or several common names and a scientific or Latin name. Some of these common names are merely local, others have a more extended use. Some few names apply to totally different species. Thus, Cottonwood in Michigan is Populus deltoides, in Idaho and Colorado Populus angustifolia, in California Populus fremontii and in Kentucky Tilia heterophylla. While it should not be forgotten that in common speech it is proper as well as convenient to call trees by their common names, yet, in view of the many uncertainties pertaining to their use, a scientific name is at times absolutely essential to the clear understanding of what is meant. Latin is the language in universal use by all scientists. No longer used by any civilized nation, it has become a dead language and consequently never changes. Its vocabulary and its constructions will a thousand years hence be the same as they are today. Being in universal use among scientists of all nationalities no confusion arises from the use of a Latin word. The Oak in Germany is known as Eiche, in France as chêne and in Spain as roble, but the Latin word Quercus is the same for all these countries.

A scientific name as applied to trees consists of at least two parts, as Quercus alba; the first named is the genus and is always written with a capital letter, the second is the species and is written with a small letter, the two names constituting the briefest possible description of the particular tree. It is customary to add to these the name or an abbreviation of the name of the person who first gave the name to the tree, as Quercus alba L., the abbreviation standing for Linnaeus. Sometimes a third name is used, as Acer saccharum nigrum, referring in this case to a variety of the ordinary Sugar Maple.

Genera which bear a relationship to each other are placed in the same family, the family name always having the characteristic ending—aceae. Related families are again grouped into orders, with the characteristic ending—ales. Orders are in like manner arranged into larger groups, called classes, and the latter into still larger groups, divisions, etc., each with its characteristic ending. Thus, Acer saccharum nigrum (Michx. f.) Britt. is classified as follows:

Division—Spermatophyta
Subdivision—Angiospermae
Class—Dicotyledoneae
Order—Sapindales
Family—Aceraceae
Genus—Acer
Species—saccharum
Variety—nigrum.

HABIT.—Habit, or the general appearance of a plant, is an important character of identification, especially as we become more and more familiar with the trees. Two main types are recognized, based on the manner of branching of the trunk, the upright and the spreading. In the one the trunk extends straight upwards without dividing, as is typical in most of the conifers, and in the other the trunk divides to form several large branches and the broad, spreading crown of most of our broad-leaf trees. The crown in either case may be regular in outline or very irregular, straggling or straight-limbed. Moreover, the tree growing in the open, where there is no crowding and there is plenty of light, may differ very greatly from the tree in the forest, where the struggle for existence becomes very keen. A short, thick trunk and low, spreading, many-branched crown characterizes the tree in the open, whereas the forest tree has a long, slender, clean trunk and a narrow crown of few branches. In the descriptions of trees in this bulletin, unless otherwise stated, the habit in the open is the one given. Again, the tree may have been injured by storm or insect at some period of its growth and its natural symmetry destroyed. Moreover, the age of a tree has a great influence on its outline, young trees being generally narrow and more or less conical, broadening out as they become older. We may say, then, that each tree has an individuality of its own, little eccentricities similar to those that make people different from one another. And just as we have little difficulty in recognizing our friends at a distance by some peculiarity of walk or action, so are we able to recognize a great many trees at a distance by some peculiarity of form or habit.

I. LEAF OUTLINES

Lanceolate.	Ovate.	Heart-shaped.	Halberd-shaped.	Linear.	Elliptical.

Oblong.	Oval.	Orbicular.	Oblanceolate.	Spatulate.	Obovate.

II. LEAF TIPS