Elements of Structural and Systematic Botany / For High Schools and Elementary College Courses

by Douglas Houghton Campbell

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 diœcious. 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).

Fig. 86.—Types of Spadicifloræ. A, inflorescence of Jack-in-the-pulpit (Arisæma, Aroideæ). The flowers (fl.) are at the base of a spike (spadix), surrounded by a sheath (spathe), which has been cut away on one side in order to show the flowers, × ½. B, leaf of the same plant, × ¼. C, vertical section of a female flower, × 2. D, three male flowers, each consisting of four stamens, × 2. E, two plants of a duck-weed (Lemna), the one at the left is in flower, × 4. F, another common species. L, Trisulea, × 1. G, male flower of E, × 25. H, optical section of the female flower, showing the single ovule (ov.), × 25. I, part of the inflorescence of the bur-reed (Sparganium), with female flowers, × ½ (Typhaceæ). J, a single, female flower, × 2. K, a ripe fruit, × 1. L, longitudinal section of the same. M, two male flowers, × 1. N, a pond-weed (Potomogeton), × 1 (Naiadaceæ). O, a single flower, × 2. P, the same, with the perianth removed, × 2. Q, fruit of the same, × 2.

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).