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Botany, in its general sense, signifies the knowledge of plants. In the earlier periods of human history plants appealed to mankind as material for food or medicine; and down to comparatively recent times botanical studies were pursued mainly in these directions. Dioscorides, a Greek, who lived in the first century of the Christian era, is the earliest writer of whom we have knowledge that can lay a claim to botanical distinction, but the medical property of plants was evidently the chief incentive to his task. It was not until the beginning of the sixteenth century that botany, in its broad sense, became a study, and Le Cluse, a French physician, who died in 1609, may be regarded as one of its patriarchs. Still the medical uses of plants were steadily kept in view. The English botanist, John Gerarde, who was a contemporary of Le Cluse, or Clusius, as botanists usually call him, wrote a remarkable work on botany,—remarkable for his time,—but this was styled a “Herbal,” as were other famous botanical works down to the beginning of the present century.

Following the year 1700, the knowledge of plants individually became so extended that systematic arrangement became desirable. The first real advance in this direction was made by Carl Von Linné, commonly known by its Latin form, Linnæus, a Swede, born in 1707, and whose talents for botanical acquirements seemed almost innate. In his twenty-third year he saw the need of a better system, and commenced at once the great work of botanical reform. He saw that plants with a certain number of stamens and pistils were correlated, and he founded classes and orders on them. Flowers with five stamens or six stamens would belong to his class pentandria or hexandria, respectively, and those with five pistils or six pistils pentagynia, or hexagynia, accordingly; and so on up to polyandria, or polygynia—many stamens or pistils—of which our common buttercup is an illustration. He further showed that two names only were all that is necessary to denote any plant, the generic name and its adjective, as, for instance, Cornus alba, the white Dogwood; and that the descriptions should be brief, covering only the essential points wherein one species of plant differed from another. This became known as the sexual system. It fairly electrified intelligent circles. People generally took to counting stamens and pistils, and large numbers took pride in being botanists because they could trace so easily the classes and orders of the plants they met. The grand old man died in 1778, and though his artificial system had to give way to a more natural method, he is justly regarded as the father of modern botany.

THE GREEN ROSE.

Flower with leaves for petals.

With the incoming of the nineteenth century, botany took a rapid start. It ceased to be a mere handmaid to the study of medicine. Chemistry, geography, teleology, and indeed the chief foundations of biology had become closely interwoven with botanical studies; and thus the progress of botany through the century has to be viewed from many standpoints.

In classification, what is known as the natural system has replaced the sexual. Plants are grouped according to their apparent relationships. Those resembling in general character the Rose form the order Rosaceæ; the Lily, Liliaceæ. Sometimes, however, a striking characteristic is adopted for the family name, as Compositæ, or compound flower, for the daisy and aster-flowered plants; Umbelliferæ, or umbel-flowering, as in carrot or parsley; Leguminosæ, having the seed vessels as legumes, like peas and beans.

HEAD OF WHITE CLOVER, WITH A BRANCH FROM THE CENTRE.

Classification has, however, derived much assistance from a wholly new branch of the science known as Morphology. This teaches that all parts of plants are modifications of other parts. What Nature may have intended to be a leaf may become a stem; the outer series of floral envelopes, or calyx, may become petals; petals may become stamens; and even pistils may become leaves, or even branches. The green rose of the florists is a case in which the leaves that should have been changed into petals to form a perfect rose flower have persisted in continuing green leaves, though masquerading as petals; and it is not unusual to find in the rose cases where the pistils have reverted to their original destination as the analogue of branches, and have started a growth from the centre of the flower. So in an orange, the carpels, or divisions, are metamorphosed primary leaves. Two series of five each make the ten divisions. Sometimes the axis starts to make another growth, as noted in the rose, but does not get far before it is arrested, and then we have a small orange inside a larger one, as in the navel orange. Just the reverse occurs sometimes. The lower series is suppressed, and only the upper one develops to a fruiting stage, when the small red oranges known as the Tangerines are the results. Illustrations of these transformations of one organ to another are frequent if we look for them. The annexed illustration shows a condition of the white clover, which, instead of the usual round head, has started on as a raceme or spike.

These wanderings from general forms were formerly regarded as monsters, of no particular use to the botanical student, but are now welcomed as guiding stars to the central features of Morphology. The importance of this branch of botany, in connection with classification, can readily be seen.

The studies in the behavior of plants have made remarkable progress during the century, and this also derives much aid from morphology. The strawberry sends out runners from which new plants are formed; but, tiring of this, eventually sends the runner upward to act as a flower stalk. What might have been but a bunch of leaves and roots at the end of the runner is now converted into a mass of flowers and pedicels at the end of a common peduncle. In some cases Nature reverses this plan. After starting the structure as an erect fruit-bearing stem, it sends it back to pierce the ground as a root should do. This is well illustrated by the peanut.

In the common Yucca, the more tropical species have erect stems; but in the form known in gardens as Adam’s needle and thread—Yucca filamentosa—the erect stem is sent down under the surface of the ground, and is then a rhizome, instead of a caudex, or stem.

PEANUT.

A pod magnified.

Modification in connection with behavior is further illustrated by the grapevine and Virginia creeper. The whole leading shoot is here pushed aside by the development of a bud at the base of the leaf, that takes the place of a leading shoot. The original leader then becomes a tendril, and serves in the economy of the plant by clinging to trees or rocks, or in coiling around other plants in support. Great progress has been made in this department of botany within recent years. Darwin has shown that the tendrils of some plants continue in motion for some time in order to find something to cling to. The grapevine especially spends a long time in this labor if there is difficulty in reaching a host. The plant preserves vital power all this time, but no sooner is support found, than nutrition is cut off, and the tendril dies, though, hard and wiry, it serves its parent plant as a support better dead than alive. The amount of nutrition spent in sustaining motion is found to be enormous. A vine that can find ready means of support grows with a much more healthy vigor than one that has difficulty in finding it. Many plants present illustrations.

Much advance has been made in the knowledge of the motions of plants as regards their various forms. Growth in plants is not continuous; but is a series of rests and advances. In other words it is rhythmic. The nodes, or knots, in the stems of grasses are resting-places. When a rest occurs, energy may be exerted in a different direction, and a change of form result. This is well illustrated by the common Dogwood of northern woods, Cornus florida on the eastern, and Cornus Nuttallii on the western slope of the American continent. On the approach of winter the leaf is reduced to a bud scale, and then rests. When spring returns these scales resume growth and appear as white bracts. In the annexed illustration the scales that served for winter protection to the buds are seen at the apex of the bracts. In other species of Dogwood the bud scales do not resume growth. Energy is spent in another direction. In this manner we have an insight as to the cause of variation, which was not perceived even so recently as Darwin’s time. We now say that variation results from varying degrees of rhythmic growth—force; and that this again is governed by varying powers of assimilation.

OUTLINE OF A WHITE DOGWOOD FLOWER (Cornus florida), SHOWING BUD-SCALES DEVELOPED TO BRACTS.

The Darwinian view, that form results from external conditions of which the plant avails itself in a struggle for existence, is still widely accepted as a leading factor in the origin of species. Those which can assume the strongest weapons of defense continue to exist under the changed conditions. The weaker ones do not survive, and we only know of them as fossils. This is termed the doctrine of natural selection.

The origin and development of plant-life, or, as it is termed, evolution, has made rapid advancement as a study during the century. That there has been an adaptation to conditions in some respects, as contended by Mr. Darwin and his followers, must be correct. The oak and other species of trees must have been formed before mistletoe and other parasites could grow on them. In the common Dodder—species of Cuscuta—the seeds germinate in the ground like ordinary plants. As soon as they find something to attach themselves to, they cut loose from mother earth and live wholly on the host. As a speculation it seems plausible that all parasites have arisen in this way. Some, like the mistletoe, having the power, at length, to have their seeds germinate on the host-plant, have left their terrestrial origin in the past uncertain. A number of parasites, however, do not seem to live wholly on the plants they attach themselves to. These are usually destitute of green color. The Indian pipe, snow plant of the Pacific Coast, and Squaw root of the Eastern States are examples; the former called ghost-flower from its paleness. These plants have little carbonaceous matter in their structure, and hence are regarded as having formed a kind of partnership with fungi. This is known now as symbiosis, or living together of dissimilar organisms, each dependent mutually. The fungus and the flowering plant in these cases are necessary to the existence of each other. They demand nitrogen instead of carbonhydroids. The Squaw root, Conopholis Americana, though attached to the subterranean portions of the trunks of trees, is probably sustained by the fungus material in the old bark, or even in the wood, rather than by the ordinary food of flowering plants. Lichens, as it is now well known, are a compound of fungi and water weeds (algæ), and this doctrine of symbiosis is regarded as one of the great advances of the century.

It is but fair to say that the doctrine of evolution by the influence of external conditions in the change of form, though widely accepted at this time, is not without strong opponents, who point to the occasional development or suppression of parts on the same plant, though the external conditions must be the same. For instance, there are flowers that have all their parts regular, as in the petals of a buttercup; and irregular, as in the snap-dragon or fox-glove. But it has been noted that irregular flowers have pendulous stalks, while the regular ones are usually erect. But once in a while, on the same plant, flowers normally drooping will become erect. In these cases the flowers are regular. In the wild snap-dragon or yellow toad-flax, Linaria vulgaris, one of the petals is developed into a long spur; the other four petals have, in early life, become connate and transformed into parts of the flower wholly unlike ordinary petals. But now and then the original petals will all develop spurs, resulting in the condition technically known as peloria.

Linnæus gave this name to this condition because it was supposed to be “monstrous,” or something opposed to law and order. Through the advance in morphological botany we have learned to regard it as the result of some normal law of development, innate to the plant, and which could as well be the regular as the occasional condition. In other words, there is no reason why Nature might not make the five-spurred flower as continuous in a wild snap-dragon as in a columbine. Many similar facts are used by those who question the Darwinian law of development.

YELLOW TOAD-FLAX.

Flower in the peloria state.

That nutrition has more to do in the evolution of form than external forces has received much aid, as a theory, from the advance during recent times of a study of the separate sexes of flowers. On coniferous trees, notably the firs, pines, and spruces, the male and female flowers are produced separately. The female, which finally yield the cones, are always borne on the most vigorous branches. When these branches have their supply of nutrition shortened and become weak, only male flowers are produced. On the other hand, branches normally weak will at times gain increased strength, and then the male flowers give female ones. This is often seen in corn fields. The generally weak tassel will have grains of corn through it. It is not infrequent to find what should normally be perfect ears on stalks weaker than usual. In these cases the upper portion of the ear will have male flowers only.

GRAINED CORN-TASSEL.

In connection with the doctrine of development, much attention has been given during the century to fertilization of flowers and the agency of insects in connection therewith. On the one hand it is contended that in all probability the flowers in the earlier periods of the world’s history had neither color nor fragrance. In this condition they were self-fertilizers, that is, were fecundated by their own pollen. In modern phraseology they were in and in breeders. When the struggle for existence became necessary, those which could get a cross with outside races became more vigorous in their progeny, and thus had an advantage in the struggle. In brief, without an occasional introduction of new blood, as it might be termed, there was danger of a race dying out. To support this view, Mr. Darwin published the result of a number of experiments. Many of them favored either side, but the average was in favor of the view that crossing was advantageous. Against this it has been urged that an average in such cases is not conclusive. If a number, though the minor number of cases, showed superiority by close breeding in his limited experiments, a new set of observations might have changed the averages, so as to make the minor figures in one instance the major in others. Again, it is contended that to increase a plant by other means than by seeds must be the closest kind of reproduction; yet some plants, coeval with the history of man, have been continued by offsets and are as strong and vigorous as ever. The Banana is an illustration. Under cultivation it produces only seedless fruits. It is raised wholly from young suckers or offsets from the roots. Mythology gives it a prominent place in the Garden of Eden, and its botanical name, Musa paradisiaca, originated in this legend.

Though much has been recorded in this line to weaken the force of the speculations that flowers late in the history of the earth developed color and sweet secretions in order to attract insects to aid in cross-fertilization, they are strongly supported by the fact that a large number of species, notably of orchids, are seldom fertilized without insect aid in pollination.

But there are anomalies even here. Some plants capture and literally eat the insects that should be regarded as their benefactors. These are classified as insectivorous plants. Some seem to catch the insects in mere sport, while in the act of conveying pollen to them. These are known as cruel plants. There are numerous illustrations of this among the families of Asclepias and Apocynum, the milk-weed family. In our gardens a Brazilian climber, Arauga, or Physianthus albens, is frequently grown for its waxy flowers and delicious odor, but the treacherous blossoms are frequently strung with the insects it has caught.

In the northern part of America a common wild flower of one of these families, Apocynum androsmæfolium, has this insect-catching habit. Numerous small insects meet death, and hang to the flowers like scalps to the wild Indian.

Considerable advance has been made in vegetable physiology, though no one has as yet been able to reach the origin of the life-power in plants. The power that enables an oak to maintain its huge branches in a horizontal direction, or that can lift or overturn huge rocks, or split them apart as the lightning rifts a tree trunk, is yet unknown. On the opposite page is an illustration of a circumstance frequently observed, wherein even a delicate root fibre can pierce a potato or other structures.

BANANA FLOWERS.

Possibly the greatest botanical advance of the century is in relation to cryptogamic plants, those low organisms which as mildews and moulds are most familiar to people generally. As microscopes increase in power, new forms are discovered. Over forty thousand species have already been described, and we may fairly say that there are nearly half as many forms of vegetable life invisible to the naked eye as can be seen by our unaided visual organs. Their wants and behaviors are very much the same as in the flowering plants or higher orders, as they are usually termed. But there is one great difference in this, that they feed mainly on nitrogen, and have no use for carbon. They care little for light, but yet have an upward tendency under certain forms, as do those which seek the light. The agarics that revel in the darkness of a coal mine, yet curve upward as heartily as a corn sprout in the open air. Just as in flowering plants, also, they are mostly innocuous, and indeed many absolutely beneficial to man, a very small portion only being poisonous, or connected with the diseases of the human race. Even in these cases their power is closely guarded by nature. The spores of fungi are found to require such a nice combination of conditions before they germinate, that, unless these occur, they will retain their vegetative power many years in a state of absolute rest. The mycelium of the mushroom, as the real plant—the cobwebby portion under ground—only starts to grow when just so many degrees of heat, neither more nor less, with just so much moisture, and the proper food, are all at hand together; and large numbers are known to be very select in the kind of food they will make use of at all. One genus, known as Cordyceps, will only start when the spore comes in contact with the head of a caterpillar. And various species of the genus will avoid a kind of caterpillar that another would enjoy. In our own country we have one that feeds on the larvae of the May Beetle, and is known as Cordyceps Melolonthæ. In Australia is a very pretty species, which takes on the appearance of the antlers of a deer. This is known as Cordyceps Andrewsii.

THE CRUEL-PLANT.

Butterfly caught in the flower.

OLD POTATO PENETRATED BY ROOTLET WITH A NEW POTATO.

The most minute of these are known as microbes. They are chiefly composed of a single cell, in the midst of which is the protoplasm, or material in which life resides, but the exact nature of which is still a mystery.

A FUNGUS (Cordyceps Andrewsii) GROWING FROM THE HEAD OF A CATERPILLAR.

A FUNGUS (Cordyceps Andrewsii) GROWING FROM THE HEAD OF A CATERPILLAR.

One of the most useful and fascinating studies in modern times is Geographical Botany. It is found to have a close relation to the history of man, and to the changes which have occurred on the surface of the earth. Plants follow man wherever he wanders; and though every other trace of man should be abolished on the American continent, the plants that came with him from the Old World would enable the future historian to follow his tracks here pretty well. No one has any historical evidence that what is now the Pacific Ocean was once land, and that the area between the Pacific Ocean and the Mississippi was once a huge sea, but botany tells the plain story. Only for botany we should not know that the land now serving as the poles was once within the tropics; and mainly by fossil gum trees on the American continent, and the existence still of a few plants common to Australia, have we the knowledge of some land connection between these distant shores. Island floras, some of the species of which are now found only in very limited areas, tell of large tracts submerged of which only the mountain peaks are left as small islands, lonely in a wide expanse of water, while other islands, with only a limited number of well known species, tell of new upheavals within modern times.

It is in these lines chiefly that botany has advanced during the century. Herbariums for dry and botanic gardens for living plants are essential. The latter are not as necessary to the study as formerly, as the facilities for travel bring the votaries of the science to distant places in a short time. Nature furnishes the living material for study at a less outlay of time and money than in the old way of growing the plants for the purpose. Few modern botanic gardens have the fame of those of the past. It is the great Herbarium of Kew, rather than the living plants, that makes that famous spot the great school for botany to-day. In our own country, the Herbariums of Cambridge, Mass.; Columbia College, New York; the National at Washington; and that of the Academy of Natural Sciences of Philadelphia, are the most famous in America.