Fig. 89. Rose pogonia. A native bog orchid with purplish-pink flowers.
Fig. 90. Yellow-fringed orchid. A bog and meadow orchid of the eastern
United States.
comprises over 6,000 species and many varieties, the overwhelming proportion of which live in the tropics. Perhaps 90 per cent of them are epiphytes, or air plants, which are perched high up on the branches or bark of trees, and take all their food and water from the air. All the native orchids of temperate North America grow in the ground, however, and their food habits are unique. They depend for food upon a microscopic organism found inside the roots of all orchids, and which helps them to take in the food from the soil. So many of these orchids are partial saprophytes, and without the associated organism they could not grow. Almost uniformly the
Fig. 91. Whorled pogonia. A woodland orchid with the leaves and flowers whorled at the apex of the stem. Fig. 92. Arethusa. The most beautiful of our bog orchids, with a fringed lip and pinkish-purple flowers which bloom about Decoration Day. Note the highly irregular flowers in this and Figs. 89-91.
Orchidaceæ have only a very few sheathing leaves, entirely without marginal teeth, and some kinds are practically leafless. The flowers, among the most gorgeous in the world, are always irregular in the sense that there is no obvious series of sepals and petals. Both these are so much transformed as to be nearly unrecognizable as such, but in some orchids there appear to be three sepals. More often of the three inner segments of the flower two are somewhat alike, while the third is quite unlike them and is known as the lip; it is among the most variable of any parts of the orchid flower. As adapted to insect visitors, the flowers of orchids are the most wonderfully developed of all plants. Because of their beauty and strange shapes, orchids have been much sought after by collectors, and explorations of tropical, fever-ridden forests have not infrequently ended in death to orchid hunters. New and rare species of them are constantly being gathered by these collectors. One expedition to New Guinea found over 1,000 kinds never before known, and in the last few decades over 4,000 new orchids have been discovered. For these plants orchid fanciers pay large sums, and a single plant of a rare one sold in London at auction for over $500. The chances of collecting such species made expeditions to the tropics frequent during the latter half of the last century.
These three families, Poaceæ, Liliaceæ, and Orchidaceæ, are perhaps the most important of all the monocotyledons, although commercially the palms, or Palmaceæ, are extensively used. It is impossible to describe or even mention all the monocotyledonous families, but a list of the more important is added. The families are arranged in the order that seems to reflect the development from simpler ones to the most complex, and is the sequence of such families used by nearly all botanists in describing the plant families of the world:
Typhaceæ—The cat-tails. Tall, reedlike swamp plants found throughout the world. One genus and about ten species.
Pandanaceæ—The screw pines. Shrubs or trees with stout, woody trunks and mostly prickly margined, long sword-shaped leaves. Confined to the Old World tropics.
Poaceæ—The grasses. Noted above.
Cyperaceæ—The sedges. Grasslike plants with solid, often triangular stems. Very often inhabitants of wet places. Throughout the world, Crex rugs are made from a species of Carex, the largest genus in the family. About 75 genera and 3,200 species.
Palmaceæ—The palms. All trees or shrubs, or sometimes climbing vines. Includes the coconut and palm-oil trees, two palms of tremendous economic importance. Inhabitants of tropical and warm regions, and only very few found in the United States. Over 130 genera and 1,200 species.
Araceæ—The arums, of which the jack-in-the-pulpit is our best-known native representative. They are nearly always herbs, often of giant size, and the great majority are found in the tropical regions. Flowers very minute, crowded together on a central column (the spadix), and this often surrounded or having at its base a leaflike appendage (the spathe). Calamus root and the skunk cabbage are also native representatives. About 105 genera and over 900 species.
Liliaceæ—The lily and related plants, noted above.
Smilaceæ—Smilax. Mostly prickly vines; our native kinds often called cat briers. Sarsaparilla comes from at least four species of Smilax. Three genera and about 300 species, mostly natives of tropical, but a few of temperate regions.
Amaryllidaceæ—The amaryllis family, noted chiefly for the sisal fiber that comes from a species of Agave, which is one of the many different kinds of century plant. The family has usually capsular fruits and black seeds, and the narcissus and amaryllis of our gardens are well-known members. About 70 genera and 800 species from tropical and warm countries; a few in temperate regions, mostly herbs.
Iridaceæ—The iris, the source of orris root, and containing some our most beautiful garden plants, the blue-eyed grass of fields, and over 50 genera and 100 species are found in this family. Nearly throughout the world, and nearly all herbs.
Musaceæ—The banana and traveler’s-tree. Giant herbs, in the banana having the largest leaves known, frequently twelve feet long and two wide. Natives of tropical and warm regions, and 4 genera and 75 species are known. Flowers often very irregular, and in Strelitzia gorgeous.
Orchidaceæ—The orchids, already noted.
While there are many thousands of plants contained in these monocotyledonous families and in the others not mentioned here, they make up only about one-third of the total number of different kinds of plants known in the world. But in grasses and sedges, in the rushes and a few other families, the number of individuals is greater than in probably any other plant family.
All the great bulk of the flowering plants not included in the monocotyledons or the gymnosperms belong to about two hundred plant families that are included in the dicotyledons. In all of them the seed sends up two seed leaves, there are generally netted-veined leaves and the parts of the flower are in fours or fives or multiples of these numbers. In such a large aggregation of plant families there are three well-marked divisions, namely, those that bear no petals or sepals, those that do bear them and where they are separated to form individual sepals or petals, and those where the petals are united to form some sort of a tubular or at least connected corolla. These divisions are perhaps best shown thus:
(a) Apetalæ—Including families where the petals are never present, and in some there is even no calyx. Examples: walnut, hickory, willow, and oaks.
(b) Polypetalæ—Petals present but separate, not forming a tubular or connected corolla. Examples: buttercup, rose, pea, apple, geranium.
(c) Gamopetalæ—Petals united and forming some sort of a tubular or connected corolla. Examples: garden primrose, gentian, salvia, mint, snapdragon, and the daisy family.
Any attempt to describe the families contained in these three divisions of the dicotyledons would take all the rest of this book and crowd out other things about plant life that must not be omitted. All that can be done here is to outline briefly a few families in each division so that we shall have fixed in our minds what the general principles of plant classification are and how these are illustrated by well-known plants. There are many books that deal with this subject in great detail and to them the student should go for further elaboration of the subject. It is one of the most interesting phases of the study of botany, but it demands a longer and more intensive study than can be included here.
(a) Apetalæ—These include families of plants that are the simplest in structure of all the dicotyledons. In all of them there are no petals and in some both petals and sepals are lacking, leaving only essential organs. Taking first those families that have neither petals nor sepals we find that most of them bear their flowers in catkins, a flower cluster familiar enough in the pussy willow. Some of these families are the following:
Juglandaceæ—Trees with compound leaves, flowers in catkins and fruits inclosed in a thick husk. Examples: walnut and hickory. Six genera and over 30 species.
Salicaceæ—Shrubs or trees with simple leaves, flowers in catkins and capsular many-seeded fruits, but no nuts. Containing only willows and poplars. Two genera and over 200 species. (Figure 93.)
Myricaceæ—Shrubs or trees with simple usually fragrant leaves, flowers in catkins and fruits one-seeded. The bayberries. Two genera and about 35 species. (Figure 94.)
These and some other families of close relationship are the least developed, in their flower structure, of any of the dicotyledons. All of them bear only the essential organs of reproduction in their very simple flowers. In the walnuts and hickories the different sexes are in different flowers on the same plant, in the willows they are even on different plants, and in Myricaceæ they are often found both ways. All of these flowers are wind-pollinated, so that they bear no honey, usually have no odor, and of course their need for showy petals for attracting insects is nil, although some pollen-eating insects visit them.
Somewhat higher in the scale of plant life are those families that, while still lacking petals, do have sepals. Their flowers are for this reason much better protected against rain or other inclement conditions, which means that they are so much the more likely to reproduce their kind. At least two of these slightly more developed families cling to the habit of bearing some of their flowers in catkins, however. Other families are also found in other parts of the world, but in North America this group is represented by:
Betulaceæ—The birch, alder, hazelnut, and hornbeam. Both staminate and pistillate flowers in catkins. Fruit a small one-seeded nut or a winged samara in the birch. All wind-pollinated. Six genera and about seventy-five species, nearly all from north temperate zone.
Fagaceæ—The oaks, beech, and chestnut. All trees or shrubs with at least their staminate flowers in catkins. Fruit inclosed in a bur (chestnut and beech) or borne in a cup (the acorns of oaks). At least five genera and about 375 species, widely distributed.
The habit of bearing some or all their flowers in catkins which flower usually before the leaves appear, and of having such flowers wholly at the mercy of precarious winds, is, if not lost, at least much less frequent in the remaining families of the apetalæ. All the others, while still without petals, do have sepals and some of these are colored so that insect visitors are likely. There are too many of these families to be enumerated here, but two of the chief are:
Ulmaceæ—The elms and hackberry. Trees or shrubs with minute greenish or yellowish flowers crowded in small clusters or in spikes. Fruit a dry nut or one-seeded and winged; or in the hackberry a drupe, one of the first evidences of even a slightly fleshy fruit in the dicotyledons. About 13 genera and 140 species, widely distributed.
Polygonaceæ—The buckwheat, knotweeds, common dock, and many other genera. Sepals often colored white or pink so the flowers are sometimes at least insect-pollinated. Flowers small and crowded in various clusters, often in a spike. Fruit an achene, a dry fruit familiar enough in the buckwheat. About 40 genera and over 800 species, mostly herbs or vines here, but often trees in the tropics.
From here on plant families leave, with some exceptions, the greenish or otherwise inconspicuous flower color, and somewhere about here they begin to rely more upon insect fertilization for the perpetuation of their kind. None of those so far mentioned have any petals to their flowers, but in the pink family or Caryophyllaceæ we find the first evidences on any considerable scale of the presence of sepals and petals, the latter usually beautifully colored. Familiar representatives of this family are the pink, carnation, chickweed, corn cockle, and the stichwort. There are over 50 genera and 1,000 species, nearly all in temperate regions.
The apetalous families appear to show a development from catkin-bearing trees with the sexes separated, and with neither petals nor sepals, through the Polygonaceæ, with often colored sepals, and the beginnings of insect fertilization. In Caryophyllaceæ, the most highly developed of them all, there are, besides the sepals, often or usually petals, and the reliance on insect fertilization is nearly complete. There are many transitional stages which cannot be included here, but they show step by step the development of the apetalous families from perfectly naked reproductive organs to the next larger group, the polypetalæ, where the process of increasingly complex flower development will now be sketched.
(b) Polypetalæ—In this large group of plant families the petals are free and quite separate, but as if they had not yet lost all the characters of the apetalæ, some families show incompletely the general characteristics of their more stable neighbors. There are, for instance, no petals in many species of the buttercup family, none in the sweet-gum tree nor in the maples, and a few others. But in spite of occasional exceptions this large group of polypetalous families do usually bear separate petals and sepals, and are among the most important of all the plant families. As they number over a hundred and contain thousands of species, all that can be done here is to mention a few typical or important ones. Just as in the apetalæ the families in this large group appear to show definite stages in development from simpler to more complex forms. But the steps are harder to trace and what appears simple characters in some plants are very complex in others.
While all the families in this group have separate petals some of them show a tendency to have united sepals, a character of perhaps some advantage and certainly very common among the still more developed gamopetalæ. Some of the families that have separate sepals agree in having the stamens inserted below the ovary. Of these the following three families may serve as types.
Nymphæaceæ—The water lilies. Aquatic plants with usually large showy flowers in which the calyx, corolla, and stamens often merge one into the other so that it is sometimes difficult to know where one series ends and the other begins. Five genera and 45 species throughout the world.
Ranunculaceæ—Buttercup family. Includes buttercups, clematis, columbine, meadow rue, golden seal, marsh-marigold, hepatica, and scores of other native plants. All herbs, except a few semiwoody vines like clematis. Sepals always present, and where no petals are found, as in marsh-marigold, colored like them. Highly irregular flowers are not uncommon, as in columbine and monkshood. The fruits are berrylike in some genera and in others dry capsules. Thirty-five genera and over 1,000 species throughout the world, but most abundant in temperate regions.
Lauraceæ—Laurel or sassafras family. Includes besides them the guava and cinnamon and camphor trees, all tropical, and the native spice-bush. All trees and shrubs with small, yellow, or greenish-yellow flowers and usually aromatic juice. Fruit a one-seeded drupe or a berry. About 40 genera and over 1,000 species, nearly all tropical, but a few in the United States.
At this point, in the sequence of plant families, there are two or three families that bear quite different fruits than any heretofore noted, and in one of them, at any rate, the four petals are in the form of a cross. So uniformly is this true that the family was for years known as the Cruciferæ, but is better known as Brassicaceæ, from Brassica, the generic name of the mustard. This large mustard family mostly has fruits known as a silique or silicle, which are pods that split into two valves; and yellow or white, rarely pinkish flowers. The juice is always somewhat acrid, familiar through the pleasant pungent taste of water-cress, but none of the family is poisonous. There are over 200 genera and nearly 2,000 species of wide distribution, and common representatives include the cress, mustard, horse-radish, garden stock, sweet alyssum, cabbage, cauliflower, brussels sprouts, radish, and turnip.
Between the Brassicaceæ and the following families there are many others that cannot be mentioned here. Somewhat farther along in the sequence are a group of families, large and important, and all having their stamens inserted around or even above the ovary, and in which the sepals are partly or wholly united. They include some of our most beautiful flowers and useful fruits. Of the many closely related families that agree in these characters the two most important are:
Rosaceæ—Rose family. In the broad sense including, besides the rose, the strawberry, blackberry, apple, pear, peach, plum, besides many herbs with wholly dry fruits. There are always five petals, five lobes to the partly united calyx, but numerous stamens. They may be herbs, shrubs, or trees, with simple or compound leaves, but these are nearly always alternately arranged. There are over 100 genera and nearly 2,000 species. Because of the size of the Rosaceæ and differences in fruit, the apple and its relatives are often included in a separate family, the Malaceæ (Figure 96), and the peaches and plums in Amygdalaceæ. The general structure of the flower is sufficiently uniform, however, for them all to have been included in Rosaceæ (Figure 97).
A prickly shrub related to the apple, which, with the plums, cherries, pears, strawberry, blackberry and hundreds of other plants are all grouped in the Rosaceæ or rose family.
Papilionaceæ—Pea family. A large family having characteristic pealike flowers, a description of which has already been given in Chapter I. They all bear legumes, a pod that splits down one side, not both, as in Brassicaceæ. Besides the pea, the bean, vetch, alfalfa, lentil, locust tree, and dozens of valuable timber trees in the tropics belong here. Flowers all showy and absolutely dependent upon insects for fertilization. Seeds highly nutritious in many genera, and the roots of nearly all have bacteria associated with them. (See chapter on Food Habits of Plants.) Three hundred and twenty-five genera and over 5,000 species of wide distribution, but most frequent in the tropics.
There are many other smaller families in different parts of the world which hover, as it were, about these two giant plant families that make definite landmarks in the scheme of plant classification. The character of having partly united sepals and numerous stamens inserted around, or even above the ovary, give to all the flowers of the Rosaceæ and related plants a general family resemblance that is very striking. The pea family, and its relatives, also have flower and fruit characters of remarkable uniformity, considering the tremendous number of species.
From this point on to the end of the polypetalæ there are scores of plant families, all agreeing in having a compound ovary, that is, one that is more than one-celled, and in also having quite distinct and separate sepals. Their agreement in these characters, however, ends all other evidences of relationship, and it is beyond the scope of this book to go into the details of each, or even a few of them. A list with some brief notes on those most important must suffice here.
Geraniaceæ—Geranium family. Includes also the common garden as well as the wild geranium. Fruit splitting into five parts. Leaves always divided or even dissected; 12 genera and 470 species, all herbs.
Anacardiaceæ—Includes the tree of heaven, sumac, poison ivy, and in the tropics, the mahogany, all trees, shrubs, or vines; 60 genera and 500 species, mostly in the tropics.
Malvaceæ—Mallow family, including, besides the marshmallow, the rose of Sharon, and cotton. They all have the stamens united into a column or tube which surrounds the style. About 40 genera and 900 species of herbs, shrubs, or trees of wide distribution.
Cactaceæ—Cactus family. Nearly all desert plants, with no leaves or practically none, and greenish stems that function as leaves and also store water. Of the greatest variety of form and always bearing numerous petals and fleshy fruits, of which the prickly pear is familiar enough. Of 40 genera and over 1,000 species, all, but a handful, come from North and South America.
Umbelliferæ (often called Ammiaceæ)—The climax of the polypetalous families, and nearly always bearing flowers in umbels. There are usually many flowers, sometimes several hundred in each cluster. Familiar examples are parsley, celery, parsnip, Queen Anne’s lace, and many others. The seeds often contain an aromatic oil, as in caraway, and some are violently poisonous, as the water hemlock. About 250 genera and over 2,000 species, all herbs, widely distributed, but most common in temperate regions.
We have seen from the foregoing the probable development of dicotyledonous plants from those simplest ones, where, as in the pines, there is merely a naked ovule between scales, through the catkin-bearing trees, without petals or sepals, and all wind-pollinated, to families where just an inconspicuous and, subsequently, a colored calyx is found, and after this the dawn of those plants that have complete and perfect flowers. Among the latter all those so far noted have separate petals, but after the Ammiaceæ, or carrot family, there appears a new character, setting off practically all other dicotyledonous plants from those already treated. This new character—and hints of it are found before it reaches the perfection found in the subsequently described families—is that of the petals being united to form some sort of a connected or, more often, a tubular corolla. The petals are represented merely by the lobes of the corolla, mostly four or five, and in many families of this group, known as the gamopetalæ, literally, united petals, this tubular corolla is irregular and often beautifully formed. In salvia, for instance, there is a hoodlike upper part overhanging the lower tubular part. Other familiar examples of these irregular corollas are the garden snapdragon, Oswego tea, skullcap, pentstemon, and many others.
(c) Gamopetalæ—The earlier families among those generally having united petals seem not yet quite sure of their new character, for a few of them hark back to the condition of having, in some genera, quite separate petals. One of the first families in this series, the Ericaceæ (Figure 98), or heath family, has several genera in which this is true, notably in the Labrador tea and the sand myrtle among native plants, and some foreign relatives. The Ericaceæ are almost exclusively shrubs or trees, but some of our native sorts, such as trailing arbutus and wintergreen, are practically herblike, although they are, strictly speaking, woody plants. The family is remarkable for containing beautiful flowered garden plants, such as the hundreds of species of South African heaths, the heather, the azaleas and rhododendrons, and our beautiful native Rhodora, about which Emerson wrote one of his most beautiful poems. The flowers in the heath family are often perfectly regular and bell-shaped, but sometimes irregular, as in azaleas and several other genera. Nearly all the family rely on microscopic organisms to get their food, and some close relatives, like the Indian pipe, are saprophytes. There are over 70 genera and 1,200 species widely distributed. Central Asia is the home of most rhododendrons and azaleas, scores of species being found in the upper reaches of the Himalayas.
The Ericaceæ are typical of many families in the first group of the gamopetalæ, in that all of them, with a few exceptions like the cranberry, have a superior ovary. That is, the petals and sepals arise from the base or below the ovary, and consequently the mature fruit in such plants is never crowned with the remains of the withered calyx, as blueberries always are and all other gamopetalæ that have an inferior ovary. The character of having an inferior or superior ovary separates the gamopetalæ into two large groups of families, the heath family and many others, with superior ovary, and a few but numerically very important families that always have an inferior ovary.
Taking first the families that all have a superior ovary, we must, for lack of space, exclude most of them from here. A few of the most important, or typical, after the Ericaceæ, are:
Primulaceæ—Primrose family. All herbs in which the stamens are as many as the lobes of the corolla and inserted on them. The flowers are quite regular. They all have some form of a capsule for fruit, which in most generally split lengthwise. Familiar examples include the garden primrose (not the wild evening primrose), yellow loosestrife, the star flower, pimpernel, shooting star, and the beautiful cyclamens. A few members of the family are slightly luminous in the dark, apparently an attraction to night-flying insects. About 28 genera and over 400 species, mostly from the northern hemisphere, a few in temperate South America and South Africa.
Gentianaceæ—Gentian family. Over 700 species in 70 genera, all bitter herbs, with opposite leaves, quite without teeth and beautiful, sometimes fringed, always regular flowers. In this and related families the stamens are of the same number as the lobes of the corolla, and always alternate with them. Gentian and sea or marsh pinks are our best-known native representatives, while some related plants are medicinal.
There are many other families in this part of the scheme of plant classification that have minor differences among themselves, but agree pretty generally in the number and position of their stamens, their superior ovary, and, on the whole, in the regular flower. Irregular and regular flowers may be recognized at once by cutting them lengthwise through the middle. In regular flowers there would be as much on one side as on the other of the dividing line, and in irregular ones quite obviously more on one side than the other. The character of all the genera in a family having irregular flowers begins to occur here with greater and sometimes exclusive frequency. In the mint family, or Lamiaceæ, nearly all of its 160 genera and over 3,000 species have two-lipped or irregular flowers. The garden salvia well illustrates the type.
The Lamiaceæ or Labiatæ, as they are often called from the two-lipped corolla, are herbs locally, but in the tropics often shrubs or trees. Almost universally they have four-sided stems and opposite leaves without stipules. The flowers may be solitary, much more often they are crowded into various kinds of clusters. The four stamens are borne on the corolla tube, and nearly always there are two long and two short ones. The family is universally fertilized by insects, and some of the flowers are wonderfully adapted for this end. Common examples, besides the salvia, are mint, thyme, skullcap, hyssop, bugle, blue curls, catnip, hedge-nettle, coleus, and Oswego tea. Most of the genera contain heavy odorous oils in their foliage, from which oil of mint, pennyroyal, lavender, rosemary, marjoram, savory and balm are the best known. These volatile oils give to members of the family their characteristic and often very beautiful odors.
There are many other families of plants, some with irregular and others with regular flowers, that appear to group themselves around the Lamiaceæ, all of which agree, in spite of individual differences, in having a superior ovary. The remaining families of the gamopetalæ, however, always have an inferior ovary, usually obvious by the insertion of petals above the ovary, and in the fruit often conspicuous by the remains of the withered calyx still clinging to the top of the fruit. Only two of the scores of families, with inferior ovary and gamopetalous corollas, will be mentioned here, both of which are important.
Rubiaceæ—Madder family. Common examples are the creeping bedstraw, the sweet woodruff, partridge berry, button bush, and bluets or quaker-ladies. All, except one of these, are herbs, but in the tropics the Rubiaceæ are nearly all shrubs or trees. Among those are the coffee, quinine, and ipecac. All the family have opposite leaves (a few verticillate) and stipules, regular flowers, with stamens as many as the corolla lobes, and alternate with them. The fruits are a drupe, berry, or capsule. Over 340 genera and 6,000 species are known almost throughout the earth.
Compositæ or Carduaceæ—The daisy family and the largest and most complex of all the plant families. As the culmination of the scheme of plant classification, they show the greatest perfection in the arrangements for cross-fertilization. For a description of their flower structure, see Chapter I, page 44, and Figures 43-45. Some of the Compositæ have no ray flowers, others are all ray flowers, but the great bulk of them bear both tubular and ray flowers in a single head. This may be single, or more commonly it is arranged in various kinds of clusters. Each head is surrounded at its base by one or more series of usually tightly overlapping bracts, incorrectly called a calyx by the unobservant. The Compositæ include over 900 genera and 11,000 species from all parts of the world. Most of them in America are herbs. Daisy, dandelion, dahlia, chrysanthemum, sunflower, boneset, chicory, lettuce, and scores of other examples could be cited, all herbs. In the tropics the Compositæ are more often trees and shrubs. The family contains many economic plants such as arnica, chamomile, artichokes, inula, and many others.
This all too brief account of the grouping of plants in families, and the sequence of these from the comparatively simple naked-seeded pines, through monocotyledons, the apetalous dicotyledons, followed by the polypetalous dicotyledons, and culminating in the Compositæ among the gamopetalous families, gives us merely a hint of what are the characters upon which plants are divided. While the details are necessarily omitted, the gradual development from naked-seeded plants, wholly at the mercy of the elements, up to those which are marvelously provided with contrivances to insure cross-fertilization, has been traced. Perhaps no other phase of botanical study offers such a rich opportunity as this, for upon the solution of some of the problems of plant classification depends the answer to many questions about the history of the earth and man’s ability to live on it. Certain of these plant families have lived on the earth hundreds of thousands of years before man first came. Others have apparently arisen comparatively recently. Many botanists believe that all the monocotyledons should be placed after the dicotyledons, as the latter may be a more ancient type than the former. How these different plant structures, some very ancient and others more recent, help to show us some of the history of the earth, will be treated, among many other evidences of a plant nature, in the chapter on “The History of the Plant Kingdom.”
FOR perhaps the largest number of readers the chief value of plants is what they furnish in the way of food, clothing, fuel, and so forth, and from this standpoint alone the study of them is more than worth while. It is unnecessary here to enumerate all the thousand and one things that we get from plants, and no attempt will be made to do so in the following pages. But certain plants like wheat, corn, cotton, jute, rubber producers, and tobacco have so shaped the life of the people, so absolutely dictated the development of whole regions of the earth’s surface that their stories are part of the history of mankind. What our cotton fields of the South, the wheat and corn fields of the Middle West, the jute in India, and the coconut palm and sugar cane in the tropics have done to dictate the economic destiny of those regions is common knowledge. Hundreds of less important plants throughout the world contribute their quota to the huge debt that man owes to the plant world. Probably no other feature of plant life offers such attractions as the study of man’s uses of plants, which is known as Economic Botany, and for which our Government maintains a large staff of experts. Some of the publications of this bureau are textbooks of the greatest value to those who grow or import plants or their products. What that amounts to in the aggregate no one can readily estimate. It certainly exceeds all other commerce combined.
Those early ancestors of ours that roamed over northern and central Europe between the periods of ice invasion, which at times made all that country uninhabitable, tell us by the relics of them found in caves that agriculture was then unknown. Living mostly by the chase and on a few wild fruits picked from the forest these half-wild and savage people wandered wherever game was plentiful and the continental glacier would permit. But there came a day when one of these races began the cultivation of some of the wild plants about them and with that day dawned the real beginning of man’s use of plants. And with that day also these simplest of our ancestors stopped their wanderings in large part and became farmers, albeit very crude ones, as their primitive stone implements show. They did not give up the chase, but their collection into more or less permanent camps or villages began with their cultivation of plants. Just when this happened no one can say, but most estimates of the time since the last ice age indicate that it could not have been much less than forty thousand years ago. And considerably before this, and long before the use of metals by man, we find these stone implements of agriculture and the probable beginnings of that great reliance upon plant life which the modern world has carried to such tremendous lengths. Unfortunately we do not know what plants these “Men of the Old Stone Age” grew in their primitive gardens, and it is thousands of years after this, and after man’s discovery of the use of metals, that we know definitely what plants he grew and how he used them. Unquestionably some of the early uses of plants, such as dyes for the face or for “rock pictures” are very ancient and are found long before any sign of agriculture, but as food in the sense of being produced food rather than that gathered from the wild, there are only the faintest traces until, in the remains of the lake dwellers in Austria, a single grain of wheat was discovered. Their metal instruments showed them to have been familiar not only with this, but with other plants, and it is well to remember that these people lived far longer ago than our most ancient historical records such as the Egyptians or Chinese. Both the latter, so far as our oldest records of them show, were an agricultural people who had enormously developed man’s uses of plants as compared with the men of the stone or bronze ages, whose agriculture must perhaps forever be a secret of the past.
The discovery of the grain of wheat in the remains of the lake dwellers tells us some things about men’s travels even in those early days, for wheat is not a wild plant there and must have come to central Europe from a great distance. Researches upon the home and antiquity of wheat are not very definite, but its occurrence as a wild plant somewhere in Mesopotamia or the vicinity appears to be indicated. The Chinese grew it 2700 B.C. and the earliest Egyptians spoke of its origin with them as due to mythical personages such as Isis, Ceres, or Triptolemus. From its ancient and perhaps rather restricted home it has gone throughout the temperate parts of the earth and now forms perhaps the most important source of food. Although many different kinds of wheat are raised in different parts of the world most of them have been derived from one wild ancestor, Triticum sativum. Forms known as hard and soft wheat and dozens of others suited to different regions or market conditions have been developed by plant breeders. As the most important of all the cereals it has been much studied, and its cultivation in America is on such a tremendous scale that we furnish a large part of the world’s supply. Russia, Argentina, and the southern part of Australia also raise large quantities. The plant is a grass and the “seed” is really a grain or fruit in which the outer husk tightly incloses the true seed.
It were perhaps well to note here that popular stories about the germination of grains of wheat taken from Egyptian mummies are not true. Wheat and even corn are sometimes given to travelers, and it is taken from these ancient Egyptian tombs. But it was not put there by the early Egyptians, as the presence of corn proves only too well. For this cereal is an American plant unknown before Columbus and 1492. Arabs and others have recently inserted various seeds in these mummies, some of which undoubtedly have germinated—hence the fable. The early Egyptians did put seeds in their mummy cases, but none have ever germinated.
The grass family furnishes this second most important cereal to all Americans and Europeans, although among inhabitants of tropical regions rice is perhaps more important than either wheat or corn. With the discovery of America the early travelers found the North American Indians, the Mexicans, and the Peruvians all growing corn and using it on a considerable scale. It must have been grown for hundreds of years before that time, as its wide distribution and many varieties testified even at that date. Its true home nor its actual wild ancestor has never been certainly determined, but a wild plant very closely related to our modern corn is found in the northern part of South America, and either there or in Central America is apparently the ancient home of corn. So much had corn entered into the life of the early Mexicans that the first Europeans to visit that country found the Mexicans making elaborate religious offerings to their corn goddess. And, as in Egypt, the tombs of the Incas of Peru contain seeds of the cereal most prized, which in the case of corn consists of several varieties. While their civilization is not as old as certain Old World races, the cultivation of corn must date back to the very beginnings of the Christian era. It is now spread throughout the world in warm regions, and as early as 1597 it was grown in China, a fact that led to the erroneous notion that China was its true home. Perhaps no fact is more conclusive as to its American origin than that corn belongs to a genus Zea, which contains only the single species mays, with perhaps one or two varieties, and that until the discovery of America Zea mays or Indian corn was unknown either as a wild or cultivated plant. Such an important cereal, if it actually were wild in the Old World, would have spread thousands of years ago as wheat did, and Columbus and his adventurous successors would not have brought from the New World a food that has since become second only to wheat.
Field corn of several different sorts, pop corn, and sweet corn were all developed by the Indians from the ancient stock, but comparatively recently the juice of the stem has been used for making corn sirup. The use of the leaves for cattle feed is known to all farmers, and from its solid stems it is now likely that some fiber good for paper making will be extracted.
Both wheat and corn are grasses that are cultivated in ordinary farm soils, but rice is derived from a grass that is nearly always grown for part of its life in water. It is taller than wheat, but not so tall as corn, and its wild home is in the tropical parts of southeastern Asia. It is still grown there in greatest quantity, and in the Philippines, while only a small part of the world’s supply comes from the New World. There are perhaps more people that rely upon rice for food than upon wheat and corn combined. It still is the principal article of diet of the inhabitants of China, Japan, India, and dozens of smaller Old World regions, while its use as a vegetable in tropical America is practically universal. A considerable part of the starch manufactured in Europe still comes from rice, and in India the intoxicating beverage arrack is made from it. The Japanese saké, a sweetish intoxicating liquor, is also made from rice. Notwithstanding its wide use it is not as nutritious as wheat or corn, being much lower in proteins than either of them.
More than 2800 years before Christ the Chinese cultivated rice, for at that time one of the emperors instituted a ceremony in which the grain plays the chief part. It has been grown on land useful to almost no other crops as it is usually subject to inundations. Some varieties, however, have been developed which will grow on uplands and these are grown even on terraced land both in China and the Philippines. It needs a heavy rainfall, however, and grows best in lands that are flooded. It is occasional dry seasons that produce the famines of India when the crop fails. The botanical name of rice is Oryza sativa, and it is known now as a wild plant in India and tropical Australia. Its introduction into Europe must have been long after wheat, for rice is not mentioned in the Bible, and was unknown in Italy before 1468, when it was first grown near Pisa. Rice paper, which some people think is made from this grain, comes from the pith of Aralia papyrifera, a tree of the rain forests of Formosa, related to our temperate region Hercules’-club.
In the chapter on what plants do with the material they take from the air and soil we found that sugar was one of the first fruits of that process. In at least two plants the overproduction of sugar is on such a great scale that our chief supplies of this substance now come from these two plants—the sugar cane, which is a tall grass, and the sugar beet. Hundreds of other plants produce surplus sugar, but for commercial purposes these two, and the sap of the sugar maple (Acer saccharum), are our chief sources of supply.
Cane sugar is an Old World grass known as Saccharum officinarum, frequently growing twelve feet high, and with a solid woody stem, quite unlike our ordinary grasses. It looks not unlike corn on a stout stem, and it is the stem which is cut and from which the sweet juice is pressed out between great rollers. The pressed-out juice goes through various processes in the course of which first molasses, then brown sugar, and finally white granulated sugar are produced.
Our consumption of sugar is now on such a scale that we scarcely realize that before the days of Shakespeare it was very scarce and expensive. Even as recently as 1840 it regularly sold in England for forty-eight shillings per hundred pounds, wholesale. At that time the total consumption in the world was only slightly over a million tons, while to-day it is over fifteen times that amount. The plant is native in tropical Asia, but just where is not known, nor are wild plants found in any quantity. It has been much modified by long cultivation, and has been reproduced by root-stocks for so long a period that it is rare for the plant to bear flower and seed. It has been known in India since before the Christian era, and was taken from there to China about 200 B. C. Neither the Greeks nor Romans knew much about it, nor do the Hebrew writings mention it. Somewhere in the Middle Ages the Arabs brought it into Egypt, Sicily, and Spain. Not until the discovery of the New World was it cultivated on any considerable scale, when the climate of Santo Domingo and Cuba and the African slaves imported to those islands afforded conditions that resulted in Cuba at least being one of the world’s chief sugar-producing countries. Sugar cane is now grown all over the earth in regions with a hot, moist climate, India and neighboring countries producing over half the world’s supply. Practically all the sugar produced in India is used there, however, so that the American tropics furnish to Europe and America about one-third of the world’s total consumption of cane sugar.
In 1840 under fifty thousand tons of beet sugar were produced, while in 1900 more sugar from this plant was made than from sugar cane. Considerably more than half this beet sugar was grown in three countries, Russia, Austria, and Germany, which explains what the great war has done to the sugar market. The plant from which beet sugar is derived is botanically the same as the common garden beet, Beta vulgaris, which is wild on sandy beaches along the Mediterranean and Caspian seas, and perhaps in India. Much cultivation has made this slender-rooted plant into the large-rooted vegetable we now have and its sugar content was much increased by Vilmorin, a French horticulturist. Many garden varieties are known, and some of these are grown in the United States, where beet sugar is produced, although in 1910 less than half a million tons were made here as against over four million tons in Europe. While the beet as a vegetable was known perhaps a century or two before the time of Christ, it was not until 1760 that its sugar content was understood, and it was nearly eighty years later before beet sugar became commercially important. Its cultivation in England on any considerable scale did not begin before the beginning of the present century.
Among the largest herbs in the world are the ordinary banana plants, now cultivated throughout the tropical regions, but originally native in the Malay Archipelago. From there it spread into India, and the early Greeks, Latins, and Arabs considered it a remarkable fruit of some Indian tree. It is actually a giant herb with a tremendous fleshy stem, formed mostly of the tightly clasping leaf bases, the blade of which is frequently ten to twelve feet long. In nature the blade splits into many segments due to tearing by the wind, a process that the plant not only tolerates but aids. The leaf has a thinner texture between its principal lateral veins, and along these weaker parts the leaf tears so that normal plants are usually almost in ribbons. The leaf expanse, without this relief, is so great that tropical storms would doubtless destroy the plant.
Many wild species of the banana are still found in tropical Old World countries, the genus Musa to which the banana belongs having over sixty-five species. There are at least three well-marked types of banana used to-day, two of them, our common yellow one and a smaller red sort being fruits of almost universal use. The remaining type is usually larger than the kinds sent to northern markets, is picked and used while still green and is always cooked before using, usually boiled as a vegetable. In this form it is known as the plantain, and is a good substitute for the potato in regions where the latter cannot be grown. Plantains are used on a large scale in all tropical countries, much more so than the yellow and red bananas which are familiar enough in northern markets. These are too sweet to be used as a staple diet, and the plantain is practically the only such diet which millions of the poorer people in the tropics ever get. There is almost no native hut but has its plantain field.
The flowers of the banana plants, all of which appear to be derived from the single species Musa sapientum or possibly also from Musa paradisiaca, are borne in a large terminal cluster which ultimately develops into the “hand” of bananas familiar in the fruit shops. The plant then dies down and a new one develops from a shoot at the base of the old stem. For countless ages this has been the only method of reproduction, and usually the banana produces no seeds. The plant is easily grown in greenhouses, one in the conservatory of the Brooklyn Botanic Garden producing 214 pounds in a single cluster consisting of 300 bananas.
Sir Walter Raleigh is usually credited with the introduction of the potato into Europe, although it appears as though the Spaniards were the first to bring the plant from America. It was brought to Ireland in 1585 or 1586 and from its wide use there became known as the Irish potato. Its native home is in southern South America, and although Columbus did not mention it after his first and second voyages, subsequent Spanish adventurers found natives on the mainland making extensive use of it. There are now several wild relatives of it in South America, but their tubers are not so large as those of Solanum tuberosum from which all the different varieties of potato have been derived. The plant is too well known to need description here, but its edible tuber, actually a stem organ, is often wrongly called a root. Figure 8 shows the tubers and true roots of the plant.
The sweet potato, which in early writings was often confused with Solanum tuberosum, is a very different plant. Its edible portion is the root of a vine very like our common morning-glory or convolvulus, and its Latin name is Ipomœa batatas. The specific name is taken from a native American word, which due to early confusion was corrupted into potato, and applied to the “Irish” potato. No one certainly knows where the sweet potato is native, but probably in tropical America. It belongs to a section of the genus Ipomœa, all the other species of which are American, and before Columbus and his followers its cultivation was unknown in the Old World. It was very soon carried by the Portuguese to Japan and other parts of the Old World, and for a time it was thought to be native there. America, however, is in all probability its ancient home, although no really wild plant has ever been found there or anywhere else. Its cultivation from very early times in America is indicated, and Columbus upon his return from the New World presented sweet potatoes to Queen Isabella.
It has been said many times that there are more uses for this plant than there are days in a year. Wood, thatch, rope, matting, an intoxicating beverage, and scores of other things are derived from different parts of this palm, but it is as a food and beverage that its chief value lies. The coconut palm is a tall tree with a dense crown of feathery but stout leaves and inhabits all parts of the tropics. It is found apparently wild along sandy shores, but its ancient home, while still unknown, is probably America. Each year the tree bears from ten to twenty fruits which are at first covered with a green and very tough fibrous husk, inside which is the seed, the coconut of commerce. In the early stages of the fruit the white meat is preceded in large part by a delicious milky liquid much used by the natives, but only rarely found in any quantity in the coconuts shipped to our markets. The meat is highly nutritious and is used on a great scale as food by millions of tropical peoples. Within the last few years a method of taking out the meat of the coconut and shipping it in a state of arrested fermentation to the north has been discovered. This product, known as copra, is produced in enormous quantities, both in the Old and the New World, particularly in India and the Philippines. From this copra a palm oil is refined, which is the chief source of the nut butter now so widely sold. Some idea of the extent of the cultivation of coconuts may be gleaned from the fact that in India and the Philippines the trees are counted by the hundreds of millions. The oil from the nuts is also largely used in cookery, in making candles, for burning in lamps, and in making certain kinds of perfume. The tree belongs to the Palmaceæ, a monocotyledonous family of plants of great commercial importance. It is known as Cocos nucifera, and the genus has over a hundred species, all of tropical American origin. Whether Cocos nucifera is American or not is still a disputed point. From the fact that it will float in sea water without injury to the seed it has been supposed that it was carried great distances by currents. It is found both wild and cultivated throughout the tropical world, and its use appears to have been known to the Asiatics probably four thousand years ago. The curious fact remains that it is the only palm that, in its wild state, is known both in the Old and New World, all others being peculiar to one hemisphere or the other. Perhaps its capacity for floating in the sea without injury may explain what is otherwise still a good deal of a mystery.
There are many other foods derived from plants, besides all the fruits and vegetables too numerous to be noted in detail here. One fact of significance seems to stand out from a study of the uses of plants by man. There are three distinct regions from which the great bulk of our food and many other useful plants have apparently come. One is the area of which Indo-China is approximately the center, and which is the ancestral home of rice, the banana, tea, sugar cane, and many other valuable plants. Somewhere in this southeastern corner of Asia there must have been a highly developed agriculture which rescued these plants from the wild, and from which they have spread throughout the world. The second region, somewhere near Mesopotamia, appears to be the cradle of wheat and a few other useful plants. And the third region is the western part of America from southern Mexico to northern Chile, where corn, tobacco, the pineapple, sweet potato, potato, the red pepper, and the tomato were all discovered with the discovery of this continent.
Alphonse de Candolle, from whose studies much of our information on the origin of cultivated plants is derived, once prepared a list of our common vegetables showing their ancient homes, their wild ancestors, and the length of time during which they have been in cultivation. With some recent additions and corrections by Dr. Orland E. White of the Brooklyn Botanic Garden, the list is printed below:
The letters indicate the probable length of cultivation.
(a) A species cultivated for more than 4,000 years.
(b) A species cultivated for more than 2,000 years.
(c) A species cultivated for less than 2,000 years.
(d) A species cultivated very anciently in America.
(e) A species cultivated in America before 1492 without giving evidence of great antiquity of culture.
(f) A species or subspecies of very recent domestication.
The following list of the common fruits also gives their native country, period of cultivation, and some additional notes about them. Those marked with a star were found in the markets of New York City by Dr. White, who also revised this list. The letters for the dates are the same as in the list of vegetables: