yx or perianth; 2d, with a perianth. In the first section we find several interesting native plants. The Clematis or Virgin's bower is a beautiful climbing plant, which supports itself by winding its petiole or leaf-bearing stems around other plants; the flowers are white and clustered in corymbs; the seed has a long silk-like fringe, which gives it a fine appearance after the blossoms have faded. This plant contains many species, and is cultivated both in this country and in Europe. At fig. 136, a, is a flower of the Clematis; b, represents its receptacle with numerous styles proceeding from it, and the petal and stamens separated, showing them to be inserted upon the receptacle.

The HELLEBORE (Helleborus) is an exotic much spoken of by classical writers. Hippocrates, one of the most ancient physicians, remarked upon its qualities; it grew about Mount Olympus, and was early known as a very poisonous plant.

(The Magnolia and Tulip-tree are among the most splendid trees of North America; they are said also to be common to China. The region of the Magnolia grandiflora extends from South Carolina to the isthmus of Darien. In some cases these trees rise to the height of 90 feet before sending off any considerable branches; the spreading top is then clothed with deep green, oblong-oval leaves, like a laurel; these are, at most seasons, enlivened by large and fragrant white flowers.

The class Polyandria, though not important for its fruits, contains some valuable medicinal plants, besides those which we have noticed.

LECTURE XXXII.

CLASS DIDYNAMIA AND TETRADYNAMIA.

THE two classes which are to afford subjects for our present observations, are founded upon the number and relative length of the stamens. In distinguishing their orders, the number of styles is not regarded, but new circumstances of distinction are introduced, viz. the seeds being enclosed in a pericarp, or destitute of this covering, and the comparative length of pods.)

α

Fig. 137.

CLASS XIII.-DIDYNAMIA.

This class has flowers with 4 stamens, two of which are longer than the other two; the stamens stand in pairs; the outer pair being longer, the inner pair shorter and converging.

The class contains two orders, Gymnospermia, (seeds naked or without a pericarp,) and Angiospermia, (seeds enclosed in a per ricarp.)

The labiate flowers are found in this class; these are monopetalous, and irregular in their outline. The term labiate is derived from the Latin labia, signifying lips; the flowers being divided at the top into two parts, resembling the lips of an animal. This tribe

Clematis-Hellebore-Magnolia-What classes are now considered?-How are their orders distinguished ?—I abiate flowers.

is divided into ringent, or gaping, and personate, or closed. These terms have been used in an indefinite manner. Linnæus called the whole tribe ringent; these he subdivided into labiate and personate. This division is illogical, since the specific term labiate, having lips, has a more general signification than the generic term ringent, lips gaping.

A few of the labiate flowers having but two stamens, are placed in the class Diandria, as the sage and mountain-mint. Yet they have, besides their two perfect stamens, the rudiments of two others, as if nature had designed them for didynamous plants. Linnæus remarks, that the insects most fond of frequenting these plants have but two perfect wings; while the rudiments of two other wings may be found concealed under a little membrane;-How wonderful are the sympathies of nature!

When you examine a labiate flower, as balm or catmint, you will observe that the arched upper lip of the petals covers the stamens, and that the lower lip hangs down, so that you can see the inside of the corolla. If you pull out the corolla, you will find the stamens attached to it, as they usually are to monopetalous corollas. The corolla shows an aperture at the base through which the pistil ascended.

The labiate plants inhabit hills and plains exposed to the sun. The aroma which escapes from their flowers, denotes their stimulating medicinal properties. Their action upon the animal economy differs according to the quantity of essential oil and of bitter principle which they contain; when the former prevails, as in mint, they are aromatic and stimulating; when the bitter principle is in excess, as in germander, they act as tonics, and strengthen the digestive organs The pericarp of the labiate flowers belongs to Mirbel's class of fruits, called cenobion.

Order Gymnospermia.

The plants in this order have labiate corollas of the ringent kind, the seeds are four, lying uncovered in the calyx; the flowers grow in whorls; the stem is four-angled, and the leaves opposite. The calyx is either five-parted, or the upper part consists of two divi sions, called lips.

At Fig. 137 is a flower of the genus Tencrium, (germander ;) the corolla is ringent, the upper lip two-cleft, the lower lip three-cleft; the stamens and pistils are incurved; the stamens are exsert through the cleavage on the upper side;-b, shows the pistil with its four uncovered, or gymnospermous seeds./

The ringent flowers generally grow in whorls at the upper part of an angular stem, the leaves standing opposite. These plants are never poisonous. Among them we find many aromatic plants, the peppermint, lavender, savory, marjorum, thyme, &c.; also many medicinal herbs, as pennyroyal, catmint, horehound, &c.; the scullcap, (Scutellaria,) which has been said to be a remedy for the hydrophobia, the modest Isanthus, (blue gentian,) and a little flower of a most beautiful blue colour, called blue curls, (Trichostema.)

Order Angiospermia.

The second order contains those plants which have many seeds, contained in a capsule. Plants of this order appear to have an af finity with some families of the clàss Pentandria. Many in addition

How divided?-Are all labiate flowers in the class Didynamia?- What is said of the properties of these plants ?-What kind of pericarps have the labiate flowers ?What plants in the order Gymnospermia ?-Describe Fig. 137-What is said of the ringent flowers 7-How is the order Angiospermia distinguished?

o the four stamens, have a fifth filament, which appears to be the rudiment of another stamen; sometimes the irregular corolla varies into a regular form, with five divisions. Among those which exhibit the imperfect fifth stamen, are the trumpet-flower, fox-glove, and Penstemon.

In this order the personate corollas are to be found, or labiate flowers with closed lips. Fig. 137, c, represents a flower of this kind, at d, is the pistil showing the capsule, or that the seeds are angio spermous. It should be observed, that in this order some few flowers may be found with bell-form and funnel-form corollas. Plants of this order differ much in their natural characters, from those of the order Gymnospermia. None of them are used in preparations for food, as are the thyme and savory of the first order, but many of them possess powerful medicinal properties, as the fox-glove, and the cancer-root, (Epiphegus.) They are in general a beautiful collection of plants; few flowers are more splendid than the Gerardia and the trumpet-flower. The Martynia is an exotic of easy cultivation, bearing a fine blossom, while its pericarp furnishes an excellent pickle.

As plants of this class are numerous in every part of the United States, you will have no difficulty in procuring them for analysis they are not usually found in blossom until the middle of summer.

Fig. 138.

CLASS XIV.-TETRADYNAMIA.

In this class we find the cruciform plants, or such as have four petals in the form of a cross; the stamens are six, four of which are longer than the remaining two. The cruciform tribe forms the natural order Cruciferæ, having flowers with a calyx of four sepals, and a corolla of four petals; each petal is fastened to the receptacle or bottom of the calyx by a narrow part called a claw, the whole exhibiting the form of a cross, hence the term cruciform, from crux, a cross. In the centre of the flower is a single pistil, long and cylindrical; the stigma is oblong and divided into two parts, which are reflexed or bent back on each side. Each petal is placed between two leaves of the calyx; this alternate position is always seen in flowers where the number of petals equals the number of leaves of the calyx. The cruciform flowers have six stamens, two of which standing opposite to each other are shorter than the other four, which always stand in pairs. This inequality in their length determines them to be in the class Tetradynamia. The germ soon becomes a long pod called a silique, or a short thick one, called silicula: this difference in the length of the pods constitutes the distinction of the two orders of the class in which they are placed. The cabbage, mustard, radish, and stockgilly-flower belong to this family. They are found, on a chemical analysis, to contain some sulphur.

*See Plate vii. Fig. 6.

Personate flowers-Class Tetradynamia-Describe the cruciform plants.

15*

Fig. 139;-at B are seen the six stamens arranged in two sets, the four at a being longer than the two at b; at care two glands between the short stamens and the germ ;-At Cis a petal consisting of a, the border, and b, the claw; at D is the pod, which is a silique; a represents the valves; b the seeds, as al

ternately fastened to the edges of the partition, (dissepiment,) which divides this kind of pericarp into two cells. The cruciform plants have dicotyledonous seeds, polypetalous corollas, and the stamens are hypogynous. They are herbs, with leaves alternate. The flowers are usually yellow or white, seldom purple.

Plants of the class Tetradynamia are never poisonous; they furnish many important vegetables for the table; their properties are antiscorbutic. The orders in this class are two, depending on the comparative length of the pods; this distinction is less definite than that which marks the orders of the class Didynamia.

Order Siliculosa.

The first Order contains plants which produce a short and round pod called a silicula; a distinction in this order is made between such plants as have pods with a notch at the top, and such as have none, or are entire. The Pepper-grass, (Lepidium,) and the shepherd's purse, (Thlaspi,) afford examples of this order. At Fig. 138, d, is a representation of the silicula or pod of the Thlaspi. The plants found here, belong to the natural family Siliquosa, the properties of which are nutritious and medicinal.

Order Siliquosæ.

The second Order contains cruciform plants with long and narrow pods; as the radish and mustard. The cabbage (Brassica) is an exotic; the turnip is a species of the same genus. At Fig. 138, a, is the wall-flower, (Cheiranthus ;) the calyx consists of four oblong sepals; the petals are obovate, spreading with claws as long as the calyx. At b, appear the six stamens divested of the petals; the germ is cylindrical, as long as the stamens; c, shows the silique or pod; the valves are concave, and a thin membranous partition divides the silique into two parts.

In this lecture we have pointed out the most important characters of the two classes which depend upon considerations derived from the number and comparative length of the stamens. Both classes we found to have two orders, not as in the preceding classes, depending upon the styles; but in the one class, on the situation of the seed as lying in the calyx, or enclosed in a seed vessel; in the other class, from the comparative length of the pericarp or pod.

Describe Fig. 139-How many orders in the class Tetradynamia?-Order Silicu .osa-Order Siliquosa-Recapitulation

LECTURE XXXIII.

CLASS XV.-MONADELPHIA.

We are now to consider the brotherhoods, as the names of the 15th and 16th classes signify; Monadelphia, meaning one, and Diadelphia two brotherhoods, in allusion to the manner in which the fila ments are connected in one or two sets. The orders in these classes lepend upon the number of stamens.

a

b

Fig. 140.

In the class Monadelphia, we include all such plants as have their filaments united in one set, forming a tube at the bottom of the corolla; in this respect, this class differs from the preceding ones, where the stamens are entirely separate; here you will observe that the anthers are separate, though the filaments are joined. We cannot in this class, as in the two preceding ones, point out any prevailing form of the corolla. The mark of distinction here is in some cases rather doubtful, the filaments being sometimes broad at their base, and yet not entirely connected.

You will recollect, that the orders depend upon the number of stamens. We have no character of the class is, filaments united, and one filament could not possess this requisite of union.

first order here, for the

Order Triandria.

This is the first order in this class; the name, you will recollect, is the same as that of the third class, signifying three stamens; but here they are united by their filaments, forming a tube. We find in this order a handsome plant, called blue-eyed grass, (Sisyrinchium ;) the three filaments have the appearance of being but one; the corolla is tubular and 6-cleft, style 1, capsule 3-celled; it belongs to the natural order Irida. The Mexican tiger-flower, genus Tigridia, is a splendid plant of this artificial order, and the natural order Irida. Its spotted flowers have given rise to the name which it bears.

Order Pentandria.

The fifth Order next occurs; this presents us with the passionflower, (Passiflora,) a climbing plant peculiar to the warm countries of America. Its immensely long, and often woody branches, attain the summits of the loftiest trees, or trail upon the ground, adorned with perennially green or falling leaves, sometimes palmate or lobed like fingers, at others appearing like the laurel.) They sustain themselves by means of undivided tendrils; and send out a succession of the most curious and splendid flowers, of which no other part of the world offers any counterpart.”* Of this genus a number of species produce fruits of great excellence; this fruit in South America is called Purchas. Sixty species of Passiflora are collected at the Linnæan garden near New York. The generic characters of the passion-flower are a 5-parted, coloured calyx, 5 petals inserted upon the calyx, 5 stamens and three pistils, the nectary, a triple crown of filaments. The very singular appearance of this flower in the arrangement of its stamens in the form of a cross, and its triple crown, * Nuttall. + See Prince's Horticulture.

The brotherhoods-Monadelphia-Orders-Order Triandria-What is said of the Passion-flower-Generic character and name.