Fig. 71. 2d. Funnel-form, (infun- | mal. Labiate corollas are said dibuliformis, from in- to be personate,* having the throat fundibulum, a funnel;) closed, or ringent,† with the throat

having a tubular base,
and a border opening

in the form of a funnel,

differing from

You

open.
have a labiate
corolla of the
ringent kind,
at Fig. 75.
The term la-
biate is also
applied to a

calyx of two

Fig. 75.

lips. Bi-labi

ate is some

funnel-shaped, times used in the same sense as in having its labiate.

tube, and bor- Different forms of Polypetalous Co

der, less sprea

ding; and from
bell-form,

in

not having its tube appear as if scooped at out the base, Fig. 72.

rollas.

pro

5th. Wheelform, (rotate, from rota, a

Fig. 77.

wheel;) having 3d. Liliaceous, a corolla with six petals, spreading gradually from the base, so as to exhibit a bell-form appearance, as in the tulip and lily.

a short border
without any tube
or with a very
short one, Fig.

74.

This kind of Lorolla may be seen in the mulkin.

6th. Labiate, (from labia, lips ;) consists of two parts, resembling the lips of a horse, or other ani

4th. Rosaceous, a corolla formed of roundish spreading petals, without claws, or with very short ones, as the rose and apple.

*From persona, a mask.
t From ringo, to grin, or gape.

Labiate corollas, how divided ?-Forms Funnel-form-Cup-shaped--Salver- of polypetalous corollas-Cruciform-Ca

form-Wheel-form.

ryophyllous-Liliaceous-Rosaceous.

The odour of flowers has its origin in the volatile oils. elaborated by the corolla; its production results from causes both external and internal, but, in both cases, equally beyond our observation. Temperature renders the odour of flowers more or less sensible; if the heat is powerful, it dissipates the volatile oils more rapidly than they are renewed: if the heat is very feeble, the volatile oils remain concentrated in the little cells where they were elaborated; under these circumstances the flowers appear to possess but little odour. But if the heat is neither too great nor too little, the volatile oils exhale without being dissipated, forming a perfumed atmosphere around the flowers.

You perceive the reason, that when you walk in a flower garden in the morning or evening, the flowers seem more fragrant than in the middle of the day. The air being more charged with humidity, is another cause of an increase of fragrance at those times; as the moisture, by penetrating the delicate tissue of the corollas, expels the volatile oils. There are some exceptions to the laws just stated; for some flowers are only odorous during the night, and others during the day. Some flowers exhale fetid odours, which attract such insects as are usually nourished by putrid animal substances Many flowers exhale sweet odours; but, however odours may differ in the sensations which they produce, it is certain, that powerful ones have a stupifying, narcotic effect upon the nerves, and that it is dangerous to respire, for any great length of time, even the most agreeable of them, in a concentrated state.

One important office of the corolla, is to secure those delicate and important organs which it encloses, the stamens and pistils, from all external injury, and to favour their development. After the germ is fertilized by the influence of the pollen, the corolla fades away, and either falls off or remains withered upon the stalk; the juices which nourished it then go to the germ, to assist in its growth, and enable it to become a perfect fruit.

Another use of the corolla seems to be, to furnish a resting-place for insects in search of honey.

The corolla is supposed by Darwin to answer the same purpose to the stamen and pistils, as the lungs in the animal system; each petal being furnished with an artery which conveys the vegetable blood to its extremities, exposing it to the light and air under a delicate moist membrane; this vegetable blood, according to his theory, is then collected and returned in correspondent veins, for

Papilionaceous-What corollas are anomalous ?-Origin of the odour of flowersOdour affected by temperature-Odour affected by moisture-Odours so netimes dis. agreeable Dangerous if respired for a long time-Office of the corolla-Darwin's heory with respect to the corolla

the sustenance of the anthers and stigmas, and for the purpose of secreting honey.

Saint Pierre* thinks the corolla is intended to collect the rays of the sun, and to reflect them upon the stamens and pistils which are placed in the centre or focus.

After all our inquiries into the uses of the corolla, we are obliged to acknowledge that it appears less important, in the economy of vegetation, than many less showy organs. It seems chiefly designed to beautify and enliven creation by the variety and elegance of its forms, the brilliancy of its colouring, and the sweetness of its perfume.

In many flowers there is an organ called the nectary, which secretes a peculiar fluid, the honey of the plant; this fluid constitutes the principal food of bees and various other species of insects.

Linnæus considered the nectary as a separate organ from the corolla; and every part of the flower which was neither stamen,

pistil, calyx, nor corolla, he called a nectary; but he undoubtedly applied the term too extensively and vaguely. The nectary is not to be confined to any particular part of the flower. Sometimes it is a mere cavity, as in the lily. The crown imperial, Fig. 79, exhibits in the claw of each of its petals a nectary of this kind; each one being filled with a sweet liquid, the secretion of the flower. If these drops are removed, others immediately take their place. The six nectariferous glands at the base of the corolla are represented in the figure; the petals are supposed to be cut in order to show the base of the flower.

In the Ranunculus, (Butter-cup,) the nectary is a production of the corolla in the form of a scale; in the violet, a process of the sanie, in the form of a horn or spur. In the Columbine, (Aquilegia,) the nectary is a separate organ from the petals, in the form of a horn. In the monk's-hood, one of the petals being concave, conceals the nectaries; they are therefore said to be hooded.

In monopetalous corollas, the tube is supposed to answer the purpose of a nectary in secreting honey. In the honeysuckle, we find at the bottom of the tube a nectariferous liquid; yet there is no appearance of any gland or organ, by which it could have been secreted, unless we suppose the tube to have performed this office.

With respect to the purpose for which honey is secreted by the nectary and other parts of the flower, there seems, among authors, to be a difference of opinion. Darwin supposes this to be the food with which the stamens and pistils are nourished, or the unripe seeds perfected. Smith asserts, that the only use of honey, with respect to the plant, is to tempt insects, which, in procuring it, scatter the dust of the anthers, and fertilize the flower, and even carry the pollen from the barren to the fertile blossoms; this is particularly the case

*This ingenious author remarks, that man seems the only animal sensible to the sweet impressions made by the colour and odour of plants upon the senses; but we think he has asserted too much. Do not the brute creation seem to enjoy, by the sense of smelling, the freshness of the verdant fields? But man is very apt to say, See all things for my use.'

66

St. Pierre's theory-Nectary-Its use-Not always a separate organ--Nectary of the Crown imperial-Different forms of nectaries-Opinions of different writers respecting

use.

in the fig tree. Although in the case of plants whose stamens and pistils are on separate flowers, we see this advantage arising from the fact of insects being attracted by the honey, yet the greater number of plants do not need any assistance in conveying pollen to the stigmas. Some imagine that honey contributes to the perfection of the stamens: but plants that do not appear to secrete honey, have perfect stamens. One thing, however, is certain with respect to this fluid, that without detriment to the plant, it yields to the industrious bee the material for the manufacture of honey, a luxury highly valued from the most ancient times. Virgil knew that bees made honey from the juices which they gathered from flowers: and we indeed, on this subject, know but little more than he has beautifully expressed in his pastorals.

Although we are ever discovering something new and wonderful in the economy of nature; and, in some cases, seem permitted to search into the hidden mysteries of her great Author, yet in our researches we are continually made sensible of the limited nature of our own faculties; and a still, small voice, seems to whisper to man, in the proudest triumphs of his reason, "Hitherto shalt thou go, but no farther."

LECTURE XIII.

STAMENS AND PISTILS.

ALTHOUGH the calyx and the corolla may be wanting, the stamens and pistils are indispensable to the perfection of the fruit. They are in most plants enclosed by the same envelope, or stand on the same receptacle; in the class Monœcia they are on different flowers which spring from one common root; and in Diœcia, they are on different flowers, springing from different roots. Yet, however distant the stamers and pistils may be, nature has provided ways by which the pollen from the staminate flowers may be conveyed to the pistillate, and there assist in perfecting the seed. That you may the better understand this curious process, and the organs by means of which it is carried on, we will examine each one separately.

Stamens.

Stamens are thread-like parts which are exterior with respect to the pistil, and interior to the corolla. They exhibit a variety of positions with respect to the pistil. These positions seldom vary in the same family, and they have therefore been taken by the celebrated Jussieu as one of the fundamental distinctions in his classification, called the "Natural method." If the stamens are inserted upon the pistil, as in umbelliferous plants, they are said to be epigynous (from epi, upon, and gynia, pistil ;) if the stamens are inserted under the germ, as in cruciform plants, they are said to be hypogynous (from hypo, under, and gynia, pistil ;) when the stamens are inserted upon the calyx, and thus stand around the germ, as in the rosaceous plants, they are said to be perigynous, (from peri, arcunċ, and gynia, pistil.)

When a corolla is monopetalous, the number of the stamens is, "sually, either equal, double, or half that of the divisions of the corolla' he stamens in such flowers never exceed twenty.

Reflections-Stamens and pistils necessary to the perfection of the fruit-Definitons of the stamen-Positions with respect to the pistil-Divisions of monoperelous torollas usually in proportion to the number of stamens.

In polypetalous corollas, the number of stamens is sometimes much greater. When they equal the divisions of the corolla, they usually alternate with these divisions. When the number of stamens is double the divisions of the corolla, half of the stamens are usually placed in the intervals of the divisions, and the remaining half be fore each lobe of the corolla, corresponding to the intervals in the divisions of the calyx. If any of the stamens are barren or without anthers, they will be found to be those which are placed before the lobes of the corolla.

In commencing the analysis of flowers according to the Linnæan system, you learned that the number of stamens, their position, relative length, and connexion, taken either singly or in combination, afford certain and distinctive marks for purposes of classification.

In the first place we find the stamens differing in number, in different plants; some plants have but one, some two, and so on till we come to ten; when they have more than ten, we find the number in the same plant varies, and therefore we cannot depend on this circumstance for further classification.

We then resort to position, and consider whether the stamens are inserted upon the calyx or the receptacle, thus furnishing an eleventh and a twelfth class.

Inequality in the length of stamens, when they are either four or six, furnishes us with a thirteenth and fourteenth class.

The connexion or union of stamens gives us the fifteenth class, where the filaments of the stamens are united in one set; the sixteenth class, where they are in two sets; the seventeenth, where the anthers of the stamens are united.

The three remaining classes of phenogamous plants are distinguished by the position of the stamens with respect to the pistils. In the eighteenth class the stamens stand on the pístil; in the nineteenth the stamens and pistils are on separate flowers on the same plant; in the twentieth they are on separate plants; and in the twenty-first they are invisible.

Parts of the Stamen.-The Filament, is so called from filum, a thread. Filaments vary in their form; some are long and slender, as in the pink; others are short and thick, as in the tulip. They are usually smooth, but in the mullein they are bearded; in the spiderwort (Tradescantia) they are covered with down. In most cases a filament supports but one anther, but sometimes it is forked and bears two or more; in some instances, many filaments have but one anther. When the filaments are enclosed in the tube of the corolla they are said to be inserted, when they extend out of it, exserted. In some cases the filament is wanting, and the anther is sessile, or immediately attached to the coralla.

In double flowers, the stamens, which seem to be intimately connected with the parts of the corolla, are changed to petals. This is the effect of cultivation, which, by affording the stamens excess of nourishment, causes them to swell out, and thus assume the form of petals. In some double flowers almost every trace of the stamens disappears; in others, it is easy to perceive the metamorphosis which they have undergone, as they retain something of their original forms. In double flowers the anthers usually disappear, which shows that the filaments have absorbed all the nourishment. In

Situation of the stamens with respect to the divisions of the corolla-Stamens used for purposes of classification-Differ in number-In their position-Stamens differ in length--In connexion-In position with respect to the pistil-Parts of the stamensFilament-Stamens changed to petals.