which the marvels of reproduction are effected. Not only is every increase of mass the result of the development of one cell from another; but, in propagation, as we here understand it, consisting in the separation of new forms of individual life, the cell is equally the efficient instrument. Within those beautiful threadlike structures in the flower which delight us by their endless wealth of form and color, are developed a definite number of single free and unconnected cells, invested with an almost indestructible yellow substance which assumes the most elegant forms. By the influence of each one of these cells-hollow cells they are called a perfect individual is to be produced, a new plant is to arise. In the centre, either of the same flower, or of another flower on the same, or a different plant, and on the variations in this particular, the Linnæan system of classification was founded, is seen a little pear-like body, from which a funnel-shaped tube is prolonged upward. In the cavity of this pear, the germen of botanists, are developed little seed-buds, each containing one large cell, the embryo sac, which itself produces the germcells; the elements of future plants. At the period of flowering, the globular pollen cells fall upon the orifice of the tube, but they cannot pass through, for the tube is wondrous small, and now they may be seen to elongate into a long thread, pierce the seed-bud, arrive at the embryonal sac, and by their magic touch arouse the germ-cell to active life, inducing in it a further cell-formation by which a seed is produced that becomes capable of carrying on a separate existence. Thus the poets may still retain their ideal fictions if they are so minded. They may sing of the triumph of the plant-cell over material nature, a mere contact becoming dynamic and suffering for the production of a new germ of separate being. They may still fable the flower-bearing plant as celebrat

ing by a kiss the most beautiful act of its renewal.

By

The scientific value of the discovery of vegetable reproduction by a peculiar cell-formation can hardly be estimated by one unacquainted with the previous state of vegetable and animal physiology. The establishment of this great law has explained what was incomprehensible; it has made brilliant with the light of truth, regions of science formerly dark with doubt; it has imposed order upon a shapeless chaos of confusedly observed phenomena. its aid we are enabled to distinguish between the reproduction of individuals and what may be called their continuation. For the former is requisite, as we have seen, the dynamizing influence of a cell of one kind, over a cell of another kind, of the sperm-cell over the germcell; the latter process, consisting in the multiplication of the original cell by division-a realization of the old paradox-occurs when we break off a slip from a tree, and from this develop a perfect plant. Here, growth takes place solely in virtue of the characteristic power which the individual cell possesses of forming new cells in its interior, which grow and arrange themselves conformably to the vesicle from which they originate. The gardener, in grafting and budding, avails himself practically of this attribute of the cell, otherwise essential as the means of growth in every plant. We especially wish to distinguish this function from the propagation; it is of the highest importance to the student that he should perceive the radical difference between the two processess; and we insist on it the more here, in the hope that some readers of these pages may be led to pursue the subject, and knowing that some of the greatest physiologists, while acknowledging the vast importance of the distinction, have not so stated it as to arrest the student's attention. Continuation of the in

dividual can occur by the action of one cell only, which exhausts its vitality in developing other cells, as it were offshoots of itself and supplementary of its vital power. For reproduction the confluence of two cells is essential, the one of which acts upon the other so as to give rise to new and separate individual existence (in itself whole) entire and distinct. It is in the first instance by establishing the universal agency of cells in the performance of these great natural functions, and afterwards by distinguishing between the modes in which they acted, and the differing laws by which they were regulated, that physiologists have succeeded in throwing light upon the sacred mysteries of nature. For the application of these principles is far from being confined to the vegetable world; the egg of the chick obeys the same laws as the seed of the plant, and thus a sublime harmony is established throughout the organic world, such as was never before dreamed of in our philosophy.

Marvellously beautiful are the provisions by which the seed is fitted to play its part in the history of the world, where it appears as at once the parent and sustainer of life, the author of vegetable, the support of animal life. So perfect, though withal so simply, is this provision, that seeds have been known to retain their vitality upwards of three thousand years, and, when planted in the earth, to germinate and bring forth. The process of germination itself is attended with special phenomena of the most impressive interest. The cells of the embryo plant require all their energy for the rapid development of its tissues by the formation of new cells; if they were diverted from their active employment in promoting growth in bulk, in order to separate and prepare their own food, it would be at the expense of the rapid development of the plant, which is the great object in view. A most beautiful provision is therefore

made for the supply of food to the embryo. The seed is supplied with a coating of albumen and starch; part of this resolves itself by a process of decomposition into a nutritive fluid, which offers to the embryo cells all the materials of growth already elaborated and prepared for use; while a part, absorbing oxygen, which combines with its carbon, creates an artificial atmosphere of carbonic acid gas, the natural food of the plant, thus at once accustoming the embryo to look forward to an independent life, and, as it were, emancipate itself from a future necessity for foreign help. The interest attaching to this peculiar function of the albumen of the seed will hardly be diminished by the reflection that it is this also which gives the seed its value to man as an article of food, and places all kinds of grain so high in the dietetic scale. Nowhere, perhaps, is the aphorism of Malpighi more applicable: Tota natura existit in minimis-nature's highest powers are seen in pigmy forms.

The fertility of resource which these powers can display, appears almost exhaustless; they overcome all material difficulties and are baffled by no physical obstacle. In the process of reproduction, not only is it necessary that the pollen-cells and the germ-cells be relieved simultaneously, so that, at the moment of effusion of the one, the other are ready to receive them, but provision must be made for those cases in which the relative position of stamen and germen is such as to apparently preclude the possibility of their being brought into contact. In many flowers, the stamens are placed at a distance around the germen, and here they may be seen to contract their circle of distance, curve over, and shed their golden shower of pollen-cells. In others the lofty pistil towers above the stamens, and then the flower gracefully droops its head, so that the pollen, in falling, will

reach its destination, or the pistil itself gently bends until it touches the stamen, and forthwith returns to its former position, instinct with animal life. But, sometimes, as in the orchids and other families of plants, the complicated structure of the organs and their irregular position seem to defy the efforts of vegetable nature and set her powers at nought. Foreign forces then come to her aid, and, while revolving in undisturbed vicissitude in the performance of their own natural duties, exert so powerful and essential an influence over the development of the plant world, that it is difficult to believe that this is not their peculiar task. For, if it be land-plants that require this foreign aid, the breeze will carry far and wide the showers of pollencells, and scatter, at least, a part of them over the productive plant; if it be water-plants that require this foreign aid, then the waves wash over the germens, and the pollen is conveyed to them. The part which the insect world takes in increasing the fertility of the plant is no less important. The bee that sucks in many a flower, flies off with a mass of pollen-cells glued to its thighs; and, upon its avidity in seeking

nectar, depends the propagation of many a tribe of plants. We may be told that a glutinous substance adheres necessarily to the bee, and that this pollen is deposited in its right place accidentally. That the hot winds of the Sahara, loaded with sand, should carry about the pollen of the date-tree, or that the rivulet should play in little ripples, are, according to the same reasoning, but simple and natural events dependent upon fixed laws of nature. What consciousness has the beetle, which in the wilds of Kamschatka, facilitates by its thefts, the increase of the lily, that on its activity depend the life of nearly the whole population of Greenland, and their sustenance through winter? What has the wind in common with the date harvest and the sustenance of millions, or the wave with the diffusion of the human race, for which it paves the way by wafting the cocoanut to distant shores? But the greater consideration will arise in most minds. If all this be but the result of natural laws, whence this marvellous combination of unintelligent forces to bring about events which have so deep an influence over the history of mankind?

FEW productions of art are more delicately beautiful than cameos, or, as some writers give the plural, camei. It is sometimes thought that a medal or medallion, or a similarly engraved article in relievo, is necessarily a cameo; but there is a needless confusion of terms here. Cameo has a special meaning, and a very pretty meaning too. It is understood that, in a good cameo, the ground shall be of a different tint from the

raised device; and the difficulty is, to find a substance which presents this difference. It will not suffice to paint the cameo, as a means of producing the diversity; this would be a sham, a factitious and imitative affair, having no value in the eyes of a person of taste.

In olden times, the cameo engravers always employed gems or valuable stones, selected with especial reference to variations in tint; but the

cheap cameos of modern days are made of shell, and the still cheaper imitations of glass. The onyx appears to have been more generally selected than any other gem-obviously in consequence of the very remarkable tints which it presents. The true onyx of the mineralogist does not mark the limit of application; for the engravers give the same name to other stones, which, though mineralogically different, are, in structure and appearance, very similar. The two chief kinds employed are the sardonyx and the carnelian onyx. The use of such stones for such a purpose is of so high antiquity, that no one can safely name the period of its introduction. There may be truth in the supposition that the art was invented in India, thence introduced into Egypt, and thence copied by the Jews, who practiced it after the Exodus from Egypt. Be that as it may, the numerous passages in the Bible relating to engraved stones and jewels are well known, and point to the existence of the art among the Israelites. "Onyx stones and stones to be set in the Ephod, and in the breastplate of the highpriest," are among the gifts which the people were commanded to bring to the tabernacle. Moses was also commanded to take two onyx stones, and engrave on them the names of the children of Israel, or rather of the twelve tribes, six on the one, and six on the other. The instructions are very precise, for they relate to the "work of an engraver in stone, like the engravings on a signet." It is true that this does not necessarily imply a production analogous to a cameo, since it may have been engraved in intaglio or sunken lines, instead of in relief. So far as can at present be judged, the Hindoos, Egyptians, Hebrews, and Persians, chiefly valued their engraved stones for the written or hieroglyphic characters wrought on them; but the more refined Greeks aimed at higher results; they sought

VOL. XII.-20

to render their engraved stones works of art, and it was then only, properly speaking, that true cameos were produced. When heads and figures were introduced upon the gems, the fancy of the Greeks had at once a wide field opened for its exercise. The Romans, likewise, practiced the art with great skill, and some of their productions, still extant, are truly wonderful. The Italians, who derived their knowledge of the art from their predecessors the Romans, are at the present day the most skilful cameo engravers; the productions of France and England in this art being less striking.

It appears that Oberstein, a small town in Prussian Saxony, furnishes the chief supply of onyxes for the cameo engravers. Some are brought from the Brazils and from the East Indies, but the European artists depend chiefly upon Oberstein. The onyx occurs in detached pieces in the ground, in rows, all separated like the nodules of flint in chalk. The value of each specimen depends mainly on the character of its markings or tints. Sometimes chalcedony and carnelian are stained to imitate real onyx; and this, indeed, forms one of the arts carried on at Oberstein. There are layers or strata in chalcedony, which, though presenting the same tint to the eye, differ in texture and compactness. The stone is capable of absorbing fluids in the direction of the strata ; but this power differs in the different strata, some of which will absorb more than others. Hence it follows that one single stone, treated with one single liquid, may be made to present as many gradations of tint as there are layers or strata, owing to their dif ference in absorptive power. This fact renders clear a statement in Pliny, which was long a matter of puzzlement. He speaks of the Roman artists boiling the onyx stones with honey for seven or eight days. This statement, once discredited, is now believed, for there are dealers in

agate, onyx, chalcedony, and carnelian, at Oberstein and Idar, who have manufactories in which analogous processes are carried on.

This onyx dyeing is very curious. It was for many years a secret in the hands of one person at Idar, who is supposed to have derived it from Italy; but the art seems now to be regularly practiced in the two towns above named. Suppose the artist to have a piece of chalcedony, or of red or yellow carnelian, which he wishes to convert into an onyx for the cameo engraver; he proceeds as follows: The stone is carefully washed and dried; it is placed in a clean vessel containing honey and water, and is there maintained at nearly a boiling heat for a period of two or three weeks; the watered honey being renewed as fast as it evaporates. This done, the stone is transferred to a vessel containing strong sulphuric acid; it is covered over with a piece of slate, and the acid is heated to 350 or 400 degrees Fahrenheit. If the stone be soft, a few hours of this powerful ordeal will suffice; but a harder specimen may require immersion in the hot acid for a whole day. The stone is then washed and dried in a kind of oven, it is polished, and it is steeped for some days in oil. The oil is afterwards removed by rubbing the stone gently with bran. Sulphuric acid is used only in the cases when a dark or onyx ground is required; if a red or carnelian ground be sought, the acid is nitric instead of sulphuric. We have spoken of one stone only, but several are operated upon at once. Now, the conjoint action of the honey, the acid, and the oil appears to be this: the honey gradually penetrates into the porous layers of the stone, and is rapidly carbonized in the pores by the acid; this carbonization deepens the tints of the dark layers in the onyx specimens, and of the red layers in the carnelian specimens; while the heat increases the opacity of the white

layers, thus rendering the contrast more striking.

There are mechanical processes carried on at Oberstein, besides this chemical treatment of a particular kind of stone for a particular purpose. Besides onyx, agate, chalcedony, and carnelian, the Oberstein lapidaries work upon amethysts and other stones and gems. The rough chalcedony or onyx stones are ground upon small mills formed of very hard sandstone, mounted on horizontal axes, and worked by water-power. The stones are generally ground until some particular layer or tint comes conspicuously to the surface; and then a polishing process succeeds. It is after this grinding that the singular chemical coloring operation is conducted, in those specimens which, whether onyx, or sardonyx, or carnelian, are to be used for cameos. A method very strange to all but those familiar with its adoption is employed for determining the value of the stones. A small fragment is broken off, and is moistened with the tongue; the buyer carefully notes the rate at which the moisture dries away; he examines to see whether it be absorbed by the stone quickly or slowly, and whether in equal or different degrees by the different layers. According to the greater or lesser rapidity of absorption, and to the equality or inequality of the absorption in different parts, so does he judge the susceptibility of the stone to receive the peculiar coloring action by means of honey, on which its fitness as a cameo material so much depends. The cameo-stones prepared at Oberstein and Idar are estimated at about $15,000 annual value.

When a suitable piece of stone reaches the hands of the cameo engraver, he has many matters to take into consideration before he can commence his artistic labors. He has to determine what his design shall be, and how far the layers of the stone will be suitable for that