Botany: The Science of Plant Life

by Norman Taylor

Some Monocotyledonous Plant Families

Of the simple plants of this group the Grass Family, or Poaceæ ([Figure 86]), is the most important, for in it are all our turf grasses, the bamboo and sugar cane, besides scores of others. Over 4,500 species are known, and they inhabit every region of the globe. The steppes of Russia and our Great Plains are predominately grassy; in the wonderful bamboo forests in the tropics are also woody representatives of this family. Certain kinds in the tropics grow as vines, with great hooked spines at the joints, so that nearly every kind of growth-form is to be found in the Poaceæ. All agree in having very small flowers, arranged in tiny spikelets, which are themselves grouped in various ways, although the inflorescence is usually some form of spike, or raceme or panicle. The individual flowers are between chaffy scales, of which several make up each spike. Always the lowest two scales are empty, and the flowers begin in the third from the bottom, or

Fig. 86. Blue-joint grass, a common grass of North America and a member of the Poaceæ. Fig. 87. Wool-grass, a tall swamp sedge popularly but incorrectly spoken of as grass. It is a member of the Cyperaceæ or Sedge family, which have usually triangular solid stems, whereas grasses have hollow round stems.

sometimes even above that. The flower is so simple that there is neither calyx nor corolla, only three stamens and one to three styles. The fruit is a grain and the Poaceæ, therefore, are the chief source of cereals. Wheat, rice, corn, oats, barley, millet, and rye, all come from grasses, and all, except corn, are natives of the Old World. They were grown for countless ages before the discovery of America, when Europeans first saw corn used by the Indians. As they are wind-pollinated, the flowers of grasses produce no honey nor colored petals, and the vast majority of them have no odor. Most of them reproduce, not only by seeds, but by rootstocks, and many of them grow so closely together that they form turf. In nearly all of them the stem is hollow, and in the largest of them, the bamboo, these hollow stems are used as water and sewer pipes, especially in India. An exception to the hollow stem is the sugar cane, from whose solid stem the juice is pressed out, that is the chief source of sugar; and our common Indian corn.

A plant of the lily family (Liliaceæ). Note the tendency to net-veined leaves in a monocotyledonous plant. Such instances are common in nature and net-veined leaves are found in certain species of smilax and most of the plants of the Arum family, containing the jack-in-the-pulpit, both monocotyledons.

Much more highly developed than the grasses is the lily family or Liliaceæ ([Figure 88]), but comprising less than 1,500 species in about 125 genera. They are nearly always herbs, but the Spanish bayonet forms a woody trunk, while the dragon tree of the Canary Islands is an extraordinary plant for a lily relative, one giant specimen of this being 80 feet tall and over 45 feet in circumference.[1] The flowers in the Liliaceæ are nearly always perfect, that is, stamens and pistils are found in the same flower. Its perianth segments are nearly always six, sometimes distinguishable as petals and sepals, but more often, as in the tulip, all colored similarly. The fruits are practically always a capsule that splits lengthwise. Perhaps the different plants in the Liliaceæ, as well as any others, illustrate the fact that plants of any particular family need not look like one another in order to be included in the same family. Nothing could be farther from resemblance than the bulb-bearing onion, the tulip, the Easter lily, the Spanish bayonet, and the dragon tree. Yet they and hundreds of other plants belong to the Liliaceæ. It cannot be overemphasized that it is flower and fruit characters that determine inclusion in any plant family, and similarity of leaves or habit may or may not accompany such characters. Among other well-known plants in the family, which is found throughout the world, are the crocus, the day lily, the dogtooth violet, hyacinth, and colchicum and aloes used in medicine. Many of them produce bulbs, such as onion, tulip, and lily and some of these contain valuable foods and drugs. The great majority of them are insect fertilized and are therefore wonderfully colored, and some furnish rich stores of honey.

But the most highly developed and interesting of all the monocotyledonous plants are the orchids ([Figures 89-92]). This family, Orchidaceæ,

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.