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Our flowering plants are divided into two main groups, the dicotyledons and the monocotyledons. These terms suggest that the division is based on the nature of the seed, which is really the case, but the groups are characterised by differences in other parts. Thus, the plants which produce seeds with two cotyledons may be known by the nature of the stem, which consists of a central pith, surrounded by wood arranged in one or more rings, and the whole enclosed in an outer epidermis or in a bark. These plants also bear leaves with netted veins, and the parts of the flower are usually in whorls of four or five or multiples of four or five. Those plants whose seeds have only one cotyledon may be known by the absence of a central pith and true bark in the stem, while the wood is arranged in scattered bundles instead of in a ring or rings. They have also, generally, leaves with parallel veins; and the parts of the flower are usually in threes or multiples of three. The following table shows these features at a glance:—

Dicotyledons	Monocotyledons
Embryo with two cotyledons.	Embryo with one cotyledon.
Stem with central pith, wood in rings or rings, and bark.	Stem with no central pith, no true bark, and wood not in rings.
Leaves with netted veins.	Leaves with parallel veins.
Parts of flower usually in fours or fives.	Parts of flower arranged in threes or multiples of three.

These two great divisions or classes are split up into sub-classes, each embracing a large number of plants with common characters; and the sub-classes are again divided into orders, and the orders into genera.

The student should always endeavour to determine the order to which any flower he finds belongs; and, if possible, the genus and the species. It is certainly a pleasure to be able to call flowers by their names, but at the same time it must be remembered that a vast deal of pleasure may be gained by the study of flowers—their peculiar structure, habits and habitats—even though their names are unknown; and the student who has learnt to recognise these characters, and to discover the relationships that exist between certain flowers of different species, is certainly much more fortunate than the one who knows abundance of names with only a meagre acquaintance with the flowers themselves.

Our table of classification gives the most important distinguishing characters of the classes, sub-classes, and orders, of a very large proportion of our wild flowers, and will enable the reader to determine the natural order of almost every one he sees. In order to show how this table is to be used we will take an imaginary example.

Let us suppose that we find a plant with a square stem; opposite, simple leaves with netted veins; flowers apparently in whorls, in the axils of the leaves; persistent calyx of five united sepals; a lipped corolla, of five united petals, two forming the lower, and three the upper lip; four stamens, attached to the corolla, two longer than the others; a superior, four-lobed ovary; and a fruit of four little nuts; then we proceed to determine the natural order to which it belongs as follows:—

The netted veins of the leaves, and the arrangement of the parts of the flower in whorls of four and five, show us at once that the plant is a dicotyledon. Then, the presence of both calyx and corolla enables us to decide that the plant belongs to Division I. of the dicotyledons—that it belongs to one of the orders 1 to 59. Noting, now, that the corolla is composed of united petals, we are enabled to fix its position in the subdivision I.B, among orders 37 to 59. Next, the superior ovary shows that it must be located in the group I.B 2—orders 44 to 59; and as the stamens are attached to the corolla, we see at once that it is not a member of order 44. Turning now to the Synopsis of the Natural Orders (p. 17), we find that the irregular flowers of this group of orders occur only in 51, 52, 53, 54, and 56. Finally, the square stem, opposite leaves, and character of the fruit, show us that the plant must belong to the order Labiatæ.

The student should, as far as possible, deal with all flowers in this manner, assigning each one to its proper order; and, if he preserves his specimens for future observation, the names of the orders should always be attached, and the plants arranged accordingly.

Again, should the reader meet with a common flower the name of which was previously known, while he is as yet ignorant as to the order to which it belongs; or, should he find a flower that he can at once identify by means of one of our illustrations; he should not rest satisfied on seeing that the name of the order is given beside the name of the plant, but turn to the synopsis, and note the distinguishing characters which determine the natural position of the plant. In this way he will cultivate the habit of careful observation; will make much more rapid progress in forming an acquaintance with plants in general, and will soon become familiar with those natural affinities which mark, more or less distinctly, a cousinship among the flowers.

To aid the reader in this part of his work we have given the name of the natural order with the name of every plant described; and, where difficulties are likely to occur in the identification of similar common species of the same genus, though perhaps only one member of the genus has been selected for description, a few notes are often included with the object of assisting in the identification of the others.

In our descriptions of wild flowers we do not always repeat those features which are common to the species of their respective orders. These features are, however, of the greatest importance; and thus it is essential that the reader makes himself acquainted with them, by referring to the synopsis of the orders, before noting those characters which are given as being more directly concerned in the determination of the species themselves. Thus, when we describe the Pasque Flower (p. 297) we do not refer to those general characters that apply to all the Ranunculaceæ or Buttercup family, and which may be seen at once by referring to p. 17, but give all those details that are necessary to enable one to distinguish between the Pasque Flower and the other members of the same order.

Dicotyledons

(Leaves with netted veins. Parts of flower generally in fours or fives or multiples of four or five)

 I. Flowers with both calyx and corolla.A. Corolla composed of free and separate petals.1. Stamens attached to base of flower, beneath the pistil—Orders 1–22.2. Stamens attached above or around the pistil—Orders 23–36.B. Corolla of united petals.1. Ovary inferior.a. Stamens on the corolla—Orders 37–41.b. Stamens on the ovary—Orders 42–43.2. Ovary superior.a. Stamens free from the corolla—Order 44.b. Stamens on the corolla—Orders 45–59.

 II. Flowers with calyx or corolla or both absent.A. Flowers with corolla absent, and, generally, with stamens and pistil in the same flower.1. Ovary superior—Orders 60–64.2. Ovary inferior—Orders 65–67.B. Corolla and calyx usually absent. Stamens and pistil usually in separate flowers.1. Flowers not in catkins—Orders 68–71.2. Flowers in catkins—Orders 72–76.

Monocotyledons

(Leaves usually with parallel veins. Parts of flower in threes or multiples of three)

 I. Perianth (see p. 11), coloured or petal-like, not scaly. (Sometimes absent.)A. Ovary inferior.1. Leaves with parallel veins—Orders 77–80.2. Leaves with netted veins—Order 81.B. Ovary superior—Orders 82–88.

 II. Flowers without perianth, enclosed in scales or husks.A. Grassy herbs, with solid stems; leaves forming unsplit sheaths round the stem; flowers in spikelets, with one to three stamens—Order 89.B. Grassy herbs, with hollow stems; leaves generally forming split sheaths round the stem; flowers generally perfect, with three stamens—Order 90.