The orders of the sixteenth, seventeenth, and eighteenth class, are founded on the number of the stamens, and they consequently receive the same names as the first thirteen classes - Triandria, Pentandria, and so on.

In the nineteenth class the orders are three, founded on the structure of the flower. - 1, AEqualis, all the florets perfect; 2, Superflua, florets of the disk perfect, those of the ray with pistil only, and hence superfluous; 3, Frustranea, florets of the disk perfect, of the ray with neither stamens or pistil; 4, Necessaria, florets on the disk with stamens, those of the ray with pistils; 5, Segregate, florets included within the common involucrum provided with proper calyces.

In the twentieth class, the orders are founded on the number of the stamens - Monandria, Diandria, &e.

The twenty-first and twenty-second classes have orders founded on the number, and other peculiarities of the stamens - Monandria, Diandria, etc.

In the twenty-third class, the orders are founded on the separation of the stamens and pistils, and are named Monoecia, Dicecia, Tricecia.

The twenty-fourth class is divided into the natural orders of Filices, or ferns; Musci, or mosses; Kepatica, or liverworts; Algae, or flags; and Fungi, or mushrooms.

These brief notes will suffice to show the principles of the system which Linnaeus propounded, and a reference to Chapter III. will explain all the details necessary to enable the student to dissect any flower, and to arrange it according to the Linnaean system, and probably this will answer the reader's purpose who simply aims at classification. But Linnaeus was sensible that his system and all systems must be imperfect, which were simply based on certain regulations of the organs of reproduction, and wished for a more natural arrangement of species. This has now been done, and the Natural System or arrangement of the vegetable world is the one on which all scientific works are now based. In it the plants are classified according to their essential organs, the growth of the stem, and the number of their cotyledons or seed-leaves.

First, the vegetable world is divided into the great primary divisions of Flowering and Flowerless plants, called in scientific language Phoenogamous and Oryptogamous. These are subdivided into three great classes.

Class I. Flowering plants with two seed lobes or cotyledons, and are therefore called Dicotyledonous; and as the stem has a distinct pith, round which the fibre is arranged in layers, the class is known also as Exogenous, or outward growing plants.

Class II. Flowering plants with only one seed-lobe are called Monocotyledons. These have stems composed of little bundles of fibres enclosed in a sheath and increase inwards; hence are called Endogenous, or inward growing. There are but few British plants, none of which are of large growth, which belong to this class.

Class III. Flowerless plants, or Acotyledons, plants destitute of seed leaves. To this class belong the ferns, mosses, liverworts, lichens, seaweeds, and fungi, with which we have nothing to do in this manual.

The first class is exemplified in nearly every British shrub. The wood is formed in rings, and is increased by internal layers. The leaves have branched and netted veins; while the leaves of the second class are not netted, but lie in parallel layers, and are easily torn into strips, as the leaves of the flags, lily, tulip, etc.

These classes are again subdivided according to their floral coverings. Class I. is divided into four divisions: -

1. Thalamifloroe, in which the flowers have separate petals, which, with the stamens, are not attached to the receptacle or thalamus. There are twenty-two British orders or families in this division.

The name of the family is derived either from some well-known species, or from some peculiar feature by which it is characterized. In the former case, the termination aceoe is added in the Latin, and aceous in English, signifying like: thus, Rosacea, rosaceous, from Rosa, rose, rose-like family. In the latter case, a term is used to indicate the family characteristic - Cruciferoe, cruciferous, or cross-bearing family, from the shape of the petals; Umbelliferoe, umbelliferous, umbel-bearing family.

1.

The Ranunculus family .

. . Ranunculaceoe.

2.

The Berberry family. . .

. . Berberidaceoe.

8.

The Water-lily family . .

. . Nymphoeaceoe.

4.

The Poppy family . . .

Rapaveraceoe.

5.

The Fumitory family . .

Fumariaceoc.

6.

The Cruciferous family . . .

. Cruciferoe.

7.

The Mignonette family

. Resedaceoe.

8.

The Bock-rose family . . ,

. Cistaceoe.

9.

The Violet family . . .

Violaceoe.

10.

The Sundew family . . .

Droseraceoe.

11.

The Milkwort family . . ,

Polygalaceoe.

12.

The Sea-heath family . . .

Frankeniaceoe.

13.

The Clove-pink family . . .

Caryophyllaceoe

14.

The Flax family .....................

Linaceoe.

15.

The Mallow family . . .

Malvaceoe.

10.

The Lime or Linden family ,

Tiliaceoe.

17.

The St. John's Wort family

Hypericaceoe.

18.

The Maple family . . .

Aceraceoe.

19.

The Crane's-bill family . .

Geraniaceoe.

20.

The Balsam family . . .

Balsaminaceoe.

21.

The Wood-sorrel family

Oxalidaceoe.

22.

The Bladder-nut family

Staphyleaceoe.

The mere repetition of the names of these families would not instruct the student much if some key was not given to them. Of the twenty-two families, four include a considerable number of genera. These are a. The Banunculus family, which is distinguished by the flowers having many stamens free from the calyx, and several carpels separated into distinct pistils. The family is nearly the same as the Linnaean class 13, Polyandria, orders Rolygynia and Pentayynia.

b. The Poppy family is distinguished also by having many stamens, but the carpels are united into a single-celled, many-seeded pistil. Two sepals soon fall off, and there are generally four petals.

c. The Cruciferous family have flowers with six stamens, two of which are shorter than the other four. Sepals and petals, each four, arranged in crosses. The fruit is either a pod or a pouch. This family is identical with the Linnaean class 15, Tetradynamia.

d. The Chickweed or Carnation family has jointed stems, with opposite and entire leaves at the joints. The flowers have long and narrow petals at the lower part, expanding at the upper, as the pink and carnation; these are termed unguiculate petals.

Families numbered 2, 17,19, and 23 contain trees only. Families numbered 12 and 14 have four or five stamens. Families 9, 10, and 20 have five stamens. No. 5, six stamens. No. 11, eight stamens. Nos. 19 and 21, ten stamens. Nos. 15 and 17 have many stamens united in one or more sets; and Nos. 3, 7, and 8 have many stamens free.

2. Calycifloroe. The distinguishing features of this sub-class are flowers with calyx and corolla. The parts of the flower are usually in fours or fives, or their multiples. The leaves are netted. The petals distinct or combined in one, and the stamens united with the calyx. In this sub-class there are twenty-six families. These are -