as far north as Clinton County, Michigan. The stout, hard pods are three to four inches long, one and one-quarter to one and one-half inches wide, and one-half inch thick. The very hard seeds are surrounded with sweet pulp, which most likely made it an inducement for some of our native animals to devour them and thus transport the undigested seeds to remote localities. The pods often remain on the trees all winter, and when dry, will float on the water of overflowed streams without any injury resulting to the hard seeds. By themselves the seeds sink at once.

CHAPTER V.
SEEDS TRANSPORTED BY WIND.

17. How pigweeds get about.—In winter we often see dead tops of lamb's-quarters and amaranths—the smooth and the prickly pigweeds—still standing where they grew in the summer. These are favorite feeding grounds for several kinds of small birds, especially when snow covers the ground.

Many of the seeds, while still enclosed in the thin, dry calyx, and these clustered on short branches, drop to the snow and are carried off by the wind. Notwithstanding the provision made for spreading the seeds by the aid of birds and the wind, the calyx around each shiny seed enables it to float also; when freed from the calyx, it drops at once to the bottom. Many kinds of dry fruits and seeds in one way or another find their way during winter to the surface of the ice-covered rivers. When the rivers break up, the seeds are carried down stream, and perhaps left to grow on dry land after the water has retired. Most of the commonest plants, the seeds of which are usually transported by water, are insignificant in appearance and without common names, or with names that are not well understood. This is one reason for omitting the description of others which are ingeniously fitted in a great variety of different ways for traveling by water.

18. Tumbleweeds.—Incidentally, the foregoing pages contain some account of seeds and fruits that are carried by the aid of wind, in connection with their distribution by other methods; but there are good reasons for giving other examples of seeds carried by the wind. There is a very common weed found on waste ground and also in fields and gardens, which on good soil, with plenty of room and light, grows much in the shape of a globe with a diameter of two to three feet. It is called Amaranthus albus in the books, and is one of the most prominent of our tumbleweeds. It does not start in the spring from seed till the weather becomes pretty warm. The leaves are small and slender, the flowers very small, with no display, and surrounded by little rigid, sharp-pointed bracts. When ripe in autumn, the dry, incurved branches are quite stiff; the main stem near the ground easily snaps off and leaves the light ball at the mercy of the winds. Such a plant is especially at home on prairies or cleared fields, where there are few large obstructions and where the wind has free access.

The mother plant, now dead, toiled busily during the heat of summer and produced thousands of little seeds. The best portion of her substance went to produce these seeds, giving each a portion of rich food for a start in life and wrapping each in a glossy black coat. Now she is ready to sacrifice the rest of her body to be tumbled about, broken in pieces, and scattered in every direction for the good of her precious progeny, most of whom will find new places, where they will stand a chance the next summer to grow into plants. Sometimes the winds are not severe enough or long enough continued, and these old skeletons are rolled into ditches, piled so high in great rows or masses against fences that some are rolled over the rest and pass on beyond. Occasionally some lodge in the tops of low trees, and many are entangled by straggling bushes. In a day or two, or in a week, or a month, the shifting wind may once more start these wrecks in other directions, to be broken up and scatter seeds along their pathway.

During the Middle Ages in southern Egypt and Arabia, and eastward, a small plant, with most of the peculiarities of our tumbleweed just described, was often seen, and was thought to be a great wonder. It was called the "rose of Jericho," though it is not a rose at all, but a first cousin to the mustard, and only a small affair at that, scarcely as large as a cabbage head. A number of other plants of this habit are well known on dry plains in various parts of the world; one of the most prominent in the northern United States is called the Russian thistle, which was introduced from Russia with flaxseed. In Dakota, often two, three, or more grow into a community, making when dry and mature a stiff ball two to three feet or more in diameter.

FIG. 25.—Mature dry plant of Russian thistle as a tumbleweed. (One-seventh natural size.)

One of our peppergrasses, Lepidium intermedium, sometimes attains the size and shape of a bushel basket; when ripe, it is blown about, sowing seeds wherever it goes. The plants of the evening primrose sometimes do likewise, also a spurge, Euphorbia [Preslii] nutans, a weed a foot to a foot and a half high.

Low hop clover, an annual with yellow flowers, which has been naturalized from Europe, has developed recently on strong clay land into a tumbleweed six inches in diameter. The tops of old witch grass, Panicum capillare, and hair grass, Agrostis hyemalis, become very brittle when ripe, and snap from the parent stem and tumble about singly or in masses, scattering seeds by the millions. I have seen piles of these thin tops larger than a load of hay where they had blown against a grove of trees, and in some cases many were caught in the tops of low trees.

FIG. 26.—The top of old witch grass as a tumbleweed. (Reduced two thirds.)

Bug seed and buffalo bur are tumbleweeds. In autumn the careful observer with an eye to this subject will be rewarded by finding many other plants that behave more or less as tumbleweeds. Especially is this the case on prairies. These are annuals, and perish at the close of the growing season. There are numerous other devices by which seeds and fruit secure transportation by the wind.

FIG. 27.—Two views of a half-pod of common locust, dry, twisted, and bent, ready for a breeze.

19. Thin, dry pods, twisted and bent, drift on the snow.—The common locust tree, Robinia Pseudacacia, blossoms and produces large numbers of thin, flat pods, which remain of a dull color even when the seeds are ripe. The pods of the locust may wait and wait, holding fast for a long time, but nothing comes to eat them. They become dry and slowly split apart, each half of the pod usually carrying every other seed. Some of the pods with the seeds still attached are torn off by the wind and fall to the ground sooner or later, according to the force of the wind. Each half-pod as it comes off is