The rose, the pink, and the bell-flower, are regular in their form; that is, there is a symmetry and equality in their parts. In a regular corolla, if we suppose the point of a compass placed upon its centre, and a circle traced around the edge of the flower, each one of its divisions will just touch the circle. There may, however, be slight inequalities in regular corollas, as in the lily we sometimes see some petals a little longer than the others; this is an exception to the general rule.

You must learn to distinguish between rules and exceptions; it is often owing to a want of this discrimination, that young persons find difficulties in understanding a science; they confound the rules and exceptions, thinking, very erroneously, that the knowledge of the one is as important as that of the other. If a clear conception of general rules be established in the mind, the exceptions or variations will be gradually learned as you apply the rules to particular cases. But if you attempt, at the commencement of the study of any science, to learn all the exceptions as well as rules, you will never obtain clear ideas up. on the subject.

You will recollect the general rules with respect to regular corollas. Irregular corollas differ so widely from these general rules, that you will be in little danger of mistaking them for exceptions; they constitute, indeed, a different natural family, though according to the artificial method of classification, they may often be placed near to regular corollas. Irregular corollas are various in their forms; the papilionaceous, which we are now considering, seem, as they stand upon their stem, to consist of an upper and under part. In examining a natural flower of this kind, a pea for example, you should first observe the calyx; this is monophyllous, that is, consisting of one entire leaf, ending in five distinct leafy points (See Fig. 100, a); the two upper ones wider than the three under ones. The calyx bends towards the lower part, as also does the peduncle, or little stalk which supports it. The peduncle is very small and flexible (See Fig. 100, g); so that the flower readily avoids a current of air, and turns its back to the wind and rain.

In examining the corolla you will see that it is polypetalous. The first piece, or large petal, covering the others and occupying the upper part of the corolla, is called the standard or banner. This petal is, evidently, designed to protect the stamens and other parts of the flower, from injuries by the weather. Upon taking off the banner you will find that it is inserted by a little process, or projecting part into the side pieces, so that

Regular corollas-Important to distinguish between rules and exceptions→ Irreguar corollas-Manner of examining a natural flower of the papilionaceous kind:

it cannot be easily separated by winds. The banner being taken off, the two side pieces, or wings, are exposed to view; they are strongly inserted into th aining part of the corolla, and their use appears to be, tirat of protecting the sides of the flower. Upon taking off the wings, you will discover the last piece of the corolla, called, on account of its form, the keel or boat. This covers and protects the stamens and pistils. Upon drawing the keel downwards, you will find the ten stamens, double in number to the petals; these stamens are joined together by the sides of their filaments, appearing like a cylinder surrounding the pistil. One of the stamens, however, does not adhere to the rest; but as the flower fades and the fruit increases, it separates and leaves an opening at the upper side, through which the germ can extend itself by gradually opening the cylinder. In the early stage of the flower, this stamen will seem not to be separated; but by carefully moving it with a pin or needle, its filament will be found unconnected with the other nine.

The germ of the papilionaceous plant extends itself into that kind of pod called a legume. It is distinguished from the Silique of the cruciform family, by having no partition in the legume. Besides, the seeds grow to one side only, being alternately attached to the edges of the two valves; but in the silique pod they are alternately attached to both edges of the partition. The legume also opens lengthwise and rolls backwards; in the silique, the valves separate and stand out from the base upwards.

The seeds of this family, as you have been already informed, have a marked scar, black spot, or line, called the hilum, by which they adhere to the pod. Near this scar there is a minute opening into the body of the seed, through which moisture is imbibed, at the period of its first growth or germination. The proper germ, or that part of the seed which is to be the future plant, continues to swell, and at length bursts through the coats of the seed, presenting between the divided halves the first true leaves, and the root, which commences its journey downwards. These divided halves of the seed are the cotyledons or seed leaves, which furnish sustenance to the plant until it is sufficiently mature to seek its own support, and then they gradually decay.

In this family we find the fine table vegetables, beans and peas; the useful medicinal plant, liquorice; the fine colouring indigo; the fragrant clover, so grateful as food to many of the domestic animals; the splendid locust tree; the elegant lupine, and the delicate and odoriferous sweet pea.

Distinction between legume and silique.

CLASS 15.

Stamens diclinious, that is, in a different flower from the pistils. Having followed Jussieu in his leading principles of arrangement, we have now arrived at that class of plants which we term imperfect, as the stamens and pistils are no longer united in the same flower. We here find a large family called Cucurbitacea, from curvus, curved; this contains the genera of the squash, gourd, cucumber, &c. which have Monoecious, and sometimes Dicecious flowers.

The Amentacea are also found in Jussieu's 15th class. This family has its staminate flowers arranged with scales, in that form of inflorescence, called an ament. The stems of these plants are woody and exogenous; you will recollect that such stems increase in diameter, by new wood being formed around the old, and that this new wood is formed from the cambium Fig. 101. which flows downwards between the wood and bark any thing which interrupts the course of this cambium would naturally cause a protuberance in the trunk, at the spot where the obstruction should take place. Fig. 101, shews a portion of the trunk of an oak surrounded by the twining stem of a wild vine; the pressure causing an accumulation of cambium, produced the protuberances which appear above the vine. Walking canes are often made of young stems which are thus knotted.

The last family in this class, and the hundredth or last order of Jussieu contains the Conifera or cone-bearing plants; their staminate flowers grow in aments, each flower being furnished with a scale which performs the office of a calyx in supporting the stamens.

The pistillate flowers form cones or strobilums. To this family belong the cedar (Juniperus), pine, cypress, &c. ; most of them contain a resinous juice, which is valuable in medicine. Turpentine is obtained from the pine; one species of the Juniperus has been supposed to have furnished the incense offered to the heathen deities.

17

LECTURE XXIII.

Use of Botanical Names.—Artificial classes and orders considered in groups.—Classes 1st and 2d.

HAVING briefly noticed some of the most conspicuous natural families of plants, according to the arrangement of Jussieu, we will now proceed to investigate in detail the Artificial or Linnæan System.

From what has been already observed, you have no doubt come to the conclusion, that this is the best method yet discovered, of finding out new plants, and of ascertaining the botanical names of those which are already known by their com mon names. If, in all countries, the common names were alike, there would be no need of any other; but the names of plants vary, in different languages, as much as other terms. We call that pen which, in France, is called plume, so we call that oak, which is there called chene.* Even in the same countries, and often in the same neighbourhoods, the common names of plants are different, but botanical names are the same, in all ages and countries; without this uniformity no permanent improvement could be made in the science. Suppose a botanist in France should send a description of la chene (the common name for oak), to his friend in America; if the latter knew something of French, he might mistake the word chene for chien, which signifies a dog, and thus he might fall into the grotesque mistake of supposing that his friend had described a wonderful species of dogs. But let the French botanist use the term quercus, and on the supposition that the American understood botany, he would at once know the meaning of the term as plainly as if it had been written oak. All botanical names are in Latin, because this is the language most universally studied; and for this reason all books on botany were for a long time written in that language. And although it is well for the learned thus to communicate with each other, by one common language, it would be unjust to deprive all who are not versed in that language, of the pleasure and advantage to be derived from this delightful science. But the learned are not only intent upon making discoveries; they also desire to impart them to others; and the fountains of botanical knowledge have, by the exertions of men of genius and learning, been made accessible to all.

* Pronounced shane.

† All the botanical works of Linnæus were written in Latin.

Use of botanical names.

In the view we are now to take of the classes and orders of Linnæus, our attention will not, as in the Natural Method, be We shall consider given to families of plants, but to genera.

each class separately, with the orders it contains, and the most remarkable genera under each order; we shall, in some cases, refer these genera to their natural families; but it has been before remarked, that the artificial system in some cases separates these families.

The Classes in the artificial system are 21.

Groups of Classes.

1st. The first ten classes are founded upon the number of stamens. 2d. Eleventh and Twelfth upon the number and insertion of stamens. 3d. Thirteenth and Fourteenth, upon number and length of stamens. 4th. Fifteenth, Sixteenth, Seventeenth and Eighteenth, upon connexion of

stamens.

5th. Nineteenth and Twentieth, upon position of stamens.

The Twenty-first class includes all plants which either have not stamens and pistils, or in which these organs are too minute to be seen, without the help of of a microscope.

The orders are founded,

1st. Upon the number of Pistils.

2d. Upon the seeds being covered, or lying uncovered in the calyx.

3d. The relative length of the pods.

4th. The comparison between the disk and ray florets of compound flowers. 5th. Number of stamens.

6th. The orders of the class Cryptogamia are distinguished by natural family characters.

NAMES OF THE ARTIFICIAL CLASSES.

1. MONANDRIA, one stamen.
2. DIANDRIA, two stamens.
3. TRIANDRIA, three stamens.
4. TETRANDRIA, four stamens.
5. PENTANDRIA, five stamens.
6. HEXANDRIA, six stamens.
7. HEPTANDRIA, seven stamens.
8. OCTANDRIA, eight stamens.
9. ENNEANDRIA, nine stamens.

10. DECANDRIA, ten stamens.

11. ICOSANDRIA, over ten stamens, situated on the calyx.

12. POLYANDRIA, over ten stamens situated on the receptacle.

13. DIDYNAMIA, four stamens, two long and two short, flowers labiate.

14. TETRADYNAMIA, six stamens, four long and two short, flowers cruciform. 15. MONADELPHIA, stamens united by their filaments into one set.

16. DIADELPHIA, stamens united by their filaments into two sets, flowers papilionaceous.

17. SYNGENESIA, five stamens united by their anthers, flowers compound. 18. GYNANDRIA, stamens growing on the pistil.

19. MONCIA, stamens and pistils on different flowers of the same plant. 20. DIŒCIA, stamens and pistils on different flowers of different plants. 21. CRYPTOGAMIA, stamens and pistils invisible.

Artificial classes considered in groups-Circumstances on which the orders are founded-Names of the artificial classes.