In the following chapter no attempt will be made to give an exhaustive account of the characteristics of each division of the monocotyledons, but only such of the most important ones as may serve to supplement our study of the special one already examined. The classification here, and this is the case throughout the spermaphytes, is based mainly upon the characters of the flowers and fruits.

The classification adopted here is that of the German botanist Eichler, and seems to the author to accord better with our present knowledge of the relationships of the groups than do the systems that are more general in this country. According to Eichler’s classification, the monocotyledons may be divided into seven groups; viz., I.LiliiflorÆ; II.EnantioblastÆ; III.SpadiciflorÆ; IV.GlumaceÆ; V.ScitamineÆ; VI.GynandrÆ; VII.HelobiÆ.

Order I.—LiliiflorÆ.

The plants of this group agree in their general structure with the adder’s-tongue, which is a thoroughly typical representative of the group; but nevertheless, there is much variation among them in the details of structure. While most of them are herbaceous forms (dying down to the ground each year), a few, among which may be mentioned the yuccas (“bear grass,” “Spanish bayonet”) of our southern states, develop a creeping or upright woody stem, increasing in size from year to year. The herbaceous forms send up their stems yearly from underground bulbs, tubers, e.g. Trillium (Fig.83, A), or thickened, creeping stems, or root stocks (rhizomes). Good examples of the last are the Solomon’s-seal (Fig.83, B), Medeola (C, D), and iris (Fig.84 A). One family, the yams (DioscoreÆ), of which we have one common native species, the wild yam (Dioscorea villosa), have broad, netted-veined leaves and are twining plants, while another somewhat similar family (SmilaceÆ) climb by means of tendrils at the bases of the leaves. Of the latter the “cat-brier” or “green-brier” is a familiar representative.

The flowers are for the most part conspicuous, and in plan like that of the adder’s-tongue; but some, like the rushes (Fig.83, E), have small, inconspicuous flowers; and others, like the yams and smilaxes, have flowers of two kinds, male and female.

The principal family of the LiliiflorÆ is the LiliaceÆ, including some of the most beautiful of all flowers. All of the true lilies (Lilium), as well as the day lilies (Funkia, Hemerocallis) of the gardens, tulips, hyacinths, lily-of-the-valley, etc., belong here, as well as a number of showy wild flowers including several species of tiger-lilies (Lilium), various species of Trillium (Fig.83, A), Solomon’s-seal (Polygonatum) (Fig.83, B), bellwort (Uvularia), and others. In all of these, except Trillium, the perigone leaves are colored alike, and the leaves parallel-veined; but in the latter the sepals are green and the leaves broad and netted-veined. The fruit of the LiliaceÆ may be either a pod, like that of the adder’s-tongue, or a berry, like that of asparagus or Solomon’s-seal.

Differing from the true lilies in having the bases of the perigone leaves adherent to the surface of the ovary, so that the latter is apparently below the flower (inferior), and lacking the inner circle of stamens, is the iris family (IridaceÆ), represented by the wild blue-flag (Iris versicolor) (Fig.84, A, E), as well as by numerous cultivated species. In iris the carpels are free above and colored like the petals (B), with the stigma on the under side. Of garden flowers the gladiolus and crocus are the most familiar examples, besides the various species of iris; and of wild flowers the little “blue-eyed grass” (Sisyrinchium).

The blue pickerel-weed (Pontederia) is the type of a family of which there are few common representatives (Fig.84, I, K).

The last family of the order is the BromeliaceÆ, all inhabitants of the warmer parts of the globe, but represented in the southern states by several forms, the commonest of which is the so-called “gray moss” (Tillandsia) (Fig.84, F, H). Of cultivated plants the pineapple, whose fruit consists of a fleshy mass made up of the crowded fruits and the fleshy flower stalks, is the best known.

Order II.—EnantioblastÆ.

The second order of the monocotyledons, EnantioblastÆ, includes very few common plants. The most familiar examples are the various species of Tradescantia (Fig.88), some of which are native, others exotic. Of the cultivated forms the commonest is one sometimes called “wandering-jew,” a trailing plant with zigzag stems, and oval, pointed leaves forming a sheath about each joint. Another common one is the spiderwort already referred to. In this the leaves are long and pointed, but also sheathing at the base. When the flowers are showy, as in these, the sepals and petals are different, the former being green. The flowers usually open but once, and the petals shrivel up as the flower fades. There are four families of the order, the spiderwort belonging to the highest one, CommelyneÆ.

Order III.—SpadiciflorÆ.

The third order of the monocotyledons, SpadiciflorÆ, is a very large one, and includes the largest and the smallest plants of the whole sub-class. In all of them the flowers are small and often very inconspicuous; usually, though not always, the male and female flowers are separate, and often on different plants. The smallest members of the group are little aquatics, scarcely visible to the naked eye, and of extremely simple structure, but nevertheless these little plants produce true flowers. In marked contrast to these are the palms, some of which reach a height of thirty metres or more.

The flowers in most of the order are small and inconspicuous, but aggregated on a spike (spadix) which may be of very large size. Good types of the order are the various aroids (AroideÆ), of which the calla (Richardia) is a very familiar cultivated example. Of wild forms the sweet-flag (Acorus), Jack-in-the-pulpit (ArisÆma) (Fig.86, A, D), skunk-cabbage (Symplocarpus), and wild calla may be noted. In ArisÆma (Fig.86, A) the flowers are borne only on the base of the spadix, and the plant is dioecious. The flowers are of the simplest structure, the female consisting of a single carpel, and the male of four stamens (C, D). While the individual flowers are destitute of a perigone, the whole inflorescence (cluster of flowers) is surrounded by a large leaf (spathe), which sometimes is brilliantly colored, this serving to attract insects. The leaves of the aroids are generally large and sometimes compound, the only instance of true compound leaves among the monocotyledons (Fig.86, B).

Probably to be regarded as reduced aroids are the duck-weeds (LemnaceÆ) (Fig.86, F, H), minute floating plants without any differentiation of the plant body into stem and leaves. They are globular or discoid masses of cells, most of them having roots; but one genus (Wolffia) has no roots nor any trace of fibro-vascular bundles. The flowers are reduced to a single stamen or carpel (Figs. E, G, H).

The cat-tail (Typha) and bur-reed (Sparganium) (Fig.86, I, L) are common representatives of the family TyphaceÆ, and the pond-weeds (Naias and Potomogeton) are common examples of the family NaiadeÆ. These are aquatic plants, completely submerged (Naias), or sometimes partially floating (Potomogeton). The latter genus includes a number of species with leaves varying from linear (very narrow and pointed) to broadly oval, and are everywhere common in slow streams.

The largest members of the group are the screw-pines (PandaneÆ) and the palms (PalmÆ). These are represented in the United States by only a few species of the latter family, confined to the southern and southwestern portions. The palmettoes (Sabal and ChamÆrops) are the best known.

Both the palms and screw-pines are often cultivated for ornament, and as is well known, in the warmer parts of the world the palms are among the most valuable of all plants. The date palm (Phoenix dactylifera) and the cocoanut (Cocos nucifera) are the best known. The apparently compound (“pinnate” or feather-shaped) leaves of many palms are not strictly compound; that is, they do not arise from the branching of an originally single leaf, but are really broad, undivided leaves, which are closely folded like a fan in the bud, and tear apart along the folds as the leaf opens.

Although these plants reach such a great size, an examination of the stem shows that it is built on much the same plan as that of the other monocotyledons; that is, the stem is composed of a mass of soft, ground tissue through which run many small isolated, fibro-vascular bundles. A good idea of this structure may be had by cutting across a corn-stalk, which is built on precisely the same pattern.

Order IV.—GlumaceÆ.

The plants of this order resemble each other closely in their habit, all having long, narrow leaves with sheathing bases that surround the slender, distinctly jointed stem which frequently has a hard, polished surface. The flowers are inconspicuous, borne usually in close spikes, and destitute of a perigone or having this reduced to small scales or hairs. The flowers are usually surrounded by more or less dry leaves (glumes, paleÆ) which are closely set, so as to nearly conceal the flowers. The flowers are either hermaphrodite or unisexual.

There are two well-marked families, the sedges (CyperaceÆ) and the grasses (GramineÆ). The former have solid, often triangular stems, and the sheath at the base of the leaves is not split. The commonest genera are Carex (Fig.87, A, G) and Cyperus, of which there are many common species, differing very little and hard to distinguish. There are several common species of Carex which blossom early in the spring, the male flowers being quite conspicuous on account of the large, yellow anthers. The female flowers are in similar spikes lower down, where the pollen readily falls upon them, and is caught by the long stigmas. In some other genera, e.g. the bulrushes (Scirpus) (Fig.87, H), the flowers are hermaphrodite, i.e. contain both stamens and pistils. The fruit (Fig.87, F) is seed-like, but really includes the wall of the ovary as well, which is grown closely to the enclosed seed. The embryo is small, surrounded by abundant endosperm (Fig.87, G). Very few of the sedges are of any economic importance, though one, the papyrus of Egypt, was formerly much valued for its pith, which was manufactured into paper.

The second family, the grasses, on the contrary, includes the most important of all food plants, all of the grains belonging here. They differ mainly from the sedges in having, generally, hollow, cylindrical stems, and the sheath of the leaves split down one side; the leaves are in two rows, while those of the sedges are in three. The flowers (Fig.87, L) are usually perfect; the stigmas, two in number and like plumes, so that they readily catch the pollen which is blown upon them. A few, like the Indian corn, have the flowers unisexual; the male flowers are at the top of the stem forming the “tassel,” and the female flowers lower down forming the ear. The “silk” is composed of the enormously lengthened stigmas. The fruits resemble those of the sedges, but the embryo is usually larger and placed at one side of the endosperm (N, em.).

While most of the grasses are comparatively small plants, a few of them are almost tree-like in their proportions, the species of bamboo (Bambusa) sometimes reaching a height of twenty to thirty metres, with stems thirty to forty centimetres in diameter.

Order V.—ScitamineÆ.

The plants of this order are all inhabitants of the warmer parts of the earth, and only a very few occur within the limits of the United States, and these confined to the extreme south. They are extremely showy plants, owing to their large leaves and brilliant flowers, and for this reason are cultivated extensively. Various species of Canna (Fig.88) are common in gardens, where they are prized for their large, richly-colored leaves, and clusters of scarlet, orange, or yellow flowers. The leafy stems arise from thick tubers or root stocks, and grow rapidly to a height of two metres or more in the larger species. The leaves, as in all the order, are very large, and have a thick midrib with lateral veins running to the margin. The young leaves are folded up like a trumpet. The flowers are irregular in form, and in Canna only a single stamen is found; or if more are present, they are reduced to petal-like rudiments. The single, perfect stamen (Fig.88, C, an.) has the filament broad and colored like the petals, and the anther attached to one side. The pistil (gy.) is also petal-like. There are three circles of leaves forming the perigone, the two outer being more or less membranaceous, and only the three inner petal-like in texture. The ovary (o) is inferior, and covered on the outside with little papillÆ that afterward form short spines on the outside of the fruit (F).

The seeds are large, but the embryo is very small. A section of a nearly ripe seed shows the embryo (em.) occupying the upper part of the embryo sac which does not nearly fill the seed and contains no endosperm. The bulk of the seed is derived from the tissue of the body of the ovule, which in most seeds becomes entirely obliterated by the growth of the embryo sac. The cells of this tissue become filled with starch, and serve the same purpose as the endosperm of other seeds. This tissue is called “perisperm.”

Of food plants belonging to this order, the banana (Musa) is much the most important. Others of more or less value are species of arrowroot (Maranta) and ginger (Zingiber).

There are three families: I.MusaceÆ (banana family); II.ZingiberaceÆ (ginger family); and III.CannaceÆ (Canna, Maranta).

Order VI.—GynandrÆ.

By far the greater number of the plants of this order belong to the orchis family (OrchideÆ), the second family of the order (ApostasieÆ), being a small one and unrepresented in the United States. The orchids are in some respects the most highly specialized of all flowers, and exhibit wonderful variety in the shape and color of the flowers, which are often of extraordinary beauty, and show special contrivances for cross-fertilization that are without parallel among flowering plants.

The flowers are always more or less bilaterally symmetrical (zygomorphic). The ovary is inferior, and usually twisted so as to turn the flower completely around. There are two sets of perigone leaves, three in each, and these are usually much alike except the lower (through the twisting of the ovary) of the inner set. This petal, known as the “lip” or “labellum,” is usually larger than the others, and different in color, as well as being frequently of peculiar shape. In many of them it is also prolonged backward in a hollow spur (see Fig.89, B). In all of the orchids except the lady’s-slippers (Cypripedium) (Fig.90, B), only one perfect stamen is developed, and this is united with the three styles to form a special structure known, as the “column” or “gynostemium” (Fig.89, B, C). The pollen spores are usually aggregated into two or four waxy masses (“pollinia,” sing. pollinium), which usually can only be removed by the agency of insects upon which all but a very few orchids are absolutely dependent for the pollination of the flowers.

In the lady-slippers there are two fertile stamens, and a third sterile one has the form of a large triangular shield terminating the column (Fig.90, C, st.).

The ovules of the orchids are extremely small, and are only partly developed at the time the flower opens, the pollen tube growing very slowly and the ovules maturing as it grows down through the tissues of the column. The ripe seeds are excessively numerous, but so fine as to look like dust.

The orchids are mostly small or moderate-sized plants, few of them being more than a metre or so in height. All of our native species, with the exception of a few from the extreme south, grow from fibrous roots or tubers, but many tropical orchids, as is well known, are “epiphytes”; that is, they grow upon the trunks and branches of trees. One genus, Vanilla, is a twining epiphyte; the fruit of this plant furnishes the vanilla of commerce. Aside from this plant, the economical value of the orchids is small, although a few of them are used medicinally, but are not specially valuable.

Of the five thousand species known, the great majority are inhabitants of the tropics, but nevertheless there are within the United States a number of very beautiful forms. The largest and showiest are the lady’s-slippers, of which we have six species at the north. The most beautiful is the showy lady’s-slipper (Cypripedium spectabile), whose large, pink and white flowers rival in beauty many of the choicest tropical orchids. Many of the Habenarias, including the yellow and purple fringed orchids, are strikingly beautiful as are the ArethuseÆ (Arethusa, Pogonia, Calopogon). The last of these (Fig.90, H) differs from all our other native orchids in having the ovary untwisted so that the labellum lies on the upper side of the flower.

A number of the orchids are saprophytic, growing in soil rich in decaying vegetable matter, and these forms are often nearly or quite destitute of chlorophyll, being brownish or yellowish in color, and with rudimentary leaves. The coral roots (Corallorhiza), of which there are several species, are examples of these, and another closely related form, the putty-root (Aplectrum) (Fig.90, A), has the flowering stems like those of Corallorhiza, but there is a single, large, plaited leaf sent up later.

Order VII.—HelobiÆ.

The last order of the monocotyledons is composed of marsh or water plants, some of which recall certain of the dicotyledons. Of the three families, the first, JuncagineÆ, includes a few inconspicuous plants with grass-like or rush-like leaves, and small, greenish or yellowish flowers (e.g. arrow-grass, Triglochin).

The second family (AlismaceÆ) contains several large and showy species, inhabitants of marshes. Of these the water-plantain (Alisma), a plant with long-stalked, oval, ribbed leaves, and a much-branched panicle of small, white flowers, is very common in marshes and ditches, and the various species of arrowhead (Sagittaria) are among the most characteristic of our marsh plants. The flowers are unisexual; the female flowers are usually borne at the base of the inflorescence, and the male flowers above. The gynoecium (Fig.91, B) consists of numerous, separate carpels attached to a globular receptacle. The sepals are green and much smaller than the white petals. The leaves (F) are broad, and, besides the thickened, parallel veins, have numerous smaller ones connecting these.

The last family is the HydrocharideÆ. They are submersed aquatics, or a few of them with long-stalked, floating leaves. Two forms, the ditch-moss (Elodea) (Fig.91, G, I) and eel-grass (Vallisneria) are very common in stagnant or slow-running water. In both of these the plants are completely submersed, but there is a special arrangement for bringing the flowers to the surface of the water. Like the arrowhead, the flowers are unisexual, but borne on different plants. The female flowers (H, L) are comparatively large, especially in Vallisneria, and are borne on long stalks, by means of which they reach the surface of the water, where they expand and are ready for pollination. The male flowers (Fig.91, J, K) are extremely small and borne, many together, surrounded by a membranous envelope, the whole inflorescence attached by a short stalk. When the flowers are ready to open, they break away from their attachment, and the envelope opens, allowing them to escape, and they immediately rise to the surface where they expand and collect in great numbers about the open female flowers. Sometimes these are so abundant during the flowering period (late in summer) that the surface of the water looks as if flour had been scattered over it. After pollination is effected, the stem of the female flower coils up like a spring, drawing the flower beneath the water where the fruit ripens.

The cells of these plants show very beautifully the circulation of the protoplasm, the movement being very marked and continuing for a long time under the microscope. To see this the whole leaf of Elodea, or a section of that of Vallisneria, may be used.