The Hair-Cap Moss, or Pigeon Wheat
The mosses are a special delight to children because they are green and beautiful before other plants have gained their greenness in the spring and after they have lost it in the fall; to the discerning eye, a mossy bank or a mossy log is a thing of beauty always. When we were children we regarded moss as a forest for fairy folk, each moss stem being a tree, and we naturally concluded that fairy forests were evergreen. We also had other diversions with pigeon wheat, for we took the fruiting stem, pulled the cap off the spore-capsule, tucked the other end of the red stem into the middle of the capsule, making a beautiful coral ring with an emerald "set." To be sure these rings were rather too delicate to last long, but there were plenty more to be had for nothing; so we made these rings into long chains which we wore as necklaces for brief and happy moments, their evanescence being one of their charms.
Pigeon wheat is a rather large moss which grows on dry knolls, usually near the margins of damp woodlands in just those places where wintergreens love to grow. In fall or winter it forms a greenish brown mass of bristling stems; in the early summer the stems are tipped with the vivid green of the new growth. The bristling appearance comes from the long sharp leaves set thickly upon the ruddy brown stems; each leaf is pretty to look at with a lens, which reveals it as thick though narrow, grooved along the middle, the edges usually armed with sharp teeth and the base clasping the stem. These leaves, although so small, are wonderfully made; during the hot, dry weather they shut up lengthwise and twist into the merest threads, in order to keep their soft, green surfaces from losing their moisture by exposure to the air; more than this, they lift themselves and huddle close to the stem, and are thus as snug and safe as may be from the effect of drought; but as soon as the rains come, they straighten back at right angles to the stem, and curve their tips downward in a joyful expanding. Bring in some of this moss and let it dry, and then drop it into a glass of water and watch this miracle of leaf movement! And yet it is no miracle but a mechanism quite automatic—and therefore—like other miracles, when once they are understood.
In early June the mossy knoll shows us the origin of the name pigeon grass or pigeon wheat, for it is then covered with a forest of shining, ruddy, stiff, little stems, each stem bearing on its tip a woolly object about the size of a grain of wheat. But it is safe to say that the pigeons and other birds enjoy our own kind of wheat better than this, which is attributed to them.
1, fruit-bearing moss stem before fertilization; 1a, the same stem after fruit is developed; a, where the ovule was before fertilization; b, fruit stem; c, spore-capsule with cap or veil upon it. 2, stem showing the starlike cups; d, the cup in which was developed the pollen which fertilized the ovule at a, this year; e, last year's cup; f, the cup of year before last; only the leaves from e to d are alive. 3, spore capsule with the cap removed, showing the lid. 5, the cap or veil removed. 4, spore capsule with lid off and shaking out the spores. 6, starlike cup in which the pollen is developed. 7, leaf of moss. 8, the top of the spore capsule showing the teeth around the edge between which the spores sift out. 9, a part of a necklace chain made of the spore capsules and their stems.
A study of one of these wheat grains reveals it as covered with a yellowish, mohair cap, ending in a golden brown peak at its tip, as if it were the original pattern of the toboggan cap; it closes loosely and downily around the stem below. This grain is the spore-capsule of the moss; the hairy cap pulls off easily when seized by its tip. This cap is present at the very beginning, even before the stem lengthens, to protect the delicate tissues of the growing spore-case; it is only through a lens that we can see it in all its silky softness. The capsule revealed by the removal of the cap is a beautiful green object, usually four-sided, set upon an elegant little pedestal where it joins the coral stem, and with a lid on its top like a sugar-bowl cover, with a point instead of a knob at its center. When the spores are ripe, this lid falls off, and then if we have a lens we may see another instance of moss mechanism. Looking at the uncovered end of the capsule, we see a row of tiny teeth around the margin, which seem to hold down an inner cover with a little raised rim. The botanists have counted these teeth and find there are 64. The teeth themselves are not important, but the openings between them are, since only through these openings can the spores escape. In fact, the capsule is a pepper-box with a grating around its upper edge instead of holes in its cover; and when it is fully ripe, instead of standing right side up, it tips over so as to shake out its spores more easily. These teeth are like the moss leaves; they swell with moisture, and thus in rainy weather they, with the inner cover, swell so that not a single spore can be shaken out. If spores should come out during the rain, they would fall among the parent plants where there is no room for growth. But when they emerge in dry weather, the wind scatters them far and wide where there is room for development.
When seen with the naked eye, the spores seem to be simply fine dust, but each dust grain is able to produce moss plants. However, the spore does not grow up into a plant like a seed, it grows into fine, green, branching threads which push along the surface of damp soil; on these threads little buds appear, each of which grows up into a moss stem.
The spore-capsule is hardly the fruit of the moss plant. If we examine the moss, we find that some stems end in yellowish cups which look almost like blossoms; on closer examination, we find that there are several of these cups, one below the other, with the stem extending up through the middle. The upper cup matured this year, the one below it last year, and so on. These cups are star-pointed, and inside, at the bottom, is a starlike cluster of leaves. Among the leaves of this star-rosette are borne the moss anthers called antheridii, too small for us to see without a high power microscope. The pollen from these anthers is blown over to other plants, some of which produce ovules at their very tips, although the ovule has no leaf-rosette to show where it is. This ovule, after receiving the pollen, grows into the spore-capsule supported on its coral stem. These—stem, capsule and all—grow up out of the mother plant, the red stem is enlarged at its base, and fits into the moss stem like a flagstaff in the socket. After the star-shaped cup has shed its pollen, the stem grows up from its center for an inch or so in height and bears new leaves, and next year will bear another starry cup.
The brown leaves on the lower part of the moss stem are dead, and only the green leaves on the upper part are living.
And this is the story of the moss cycle:
1. A plant with an ovule at its tip; another plant with a star-cup holding the moss pollen which is sifted by wind over to the waiting egg.
2. The egg or ovule as soon as fertilized develops into a spore-capsule, and is lifted up into the world on a beautiful shining stem and is protected by a silky cap.
3. The cap comes off; the lid of the spore-case falls off, the spores are shaken out and scattered by the wind.
4. Those spores that find fitting places grow into a net of green threads.
5. These green threads send up moss stems which repeat the story.
The Hair-Cap Moss
Leading thought—The mosses, like the butterfly and the fern, have several stages in their development. The butterfly stages are the egg, the caterpillar, the chrysalis, the butterfly. The moss stages are the egg (or ovule), the spores, the branching green threads, the moss plants with their green foliage. In June we can easily find all these stages, except perhaps the branching thread stage.
Method—The children should bring to the schoolroom a basin of moss in its fruiting stage; or still better, go with them to a knoll covered with moss. Incidentally tell them that this moss, when dried, is used by the Laplanders for stuffing their pillows, and that the bears use it for their beds. Once, a long time ago, people believed that a plant, by the shape of its leaf or flower, indicated its nature as a medicine, and as this moss looked like hair, the water in which it was steeped was used as a hair tonic.
1. Take a moss stem with a grain of pigeon wheat at the end. Examine the lower part of the stalk. How are the leaves arranged on it? Examine one of the little leaves through a lens and describe its shape, its edges, and the way it joins the stem. Are the lower leaves the same color as the upper ones? Why?
2. Describe the pretty shining stem of the fruit, which is called the pedicel. Is it the same color for its entire length? Can you pull it easily from the main plant? Describe how its base is embedded in the tip of the plant.
3. Note the silken cap on a grain of the pigeon wheat. This is called the veil. Is it all the same color? Is it grown fast to the plant at its lower margin? Take it by the tip, and pull it off. Is this done easily? Describe what it covers. This elegant little green vase is called a spore-capsule. How many sides has it? Describe its base which stands upon the stem. Describe the little lid. Pull off the lid; is there another lid below it? Can you see the tiny teeth around the edge which hold this lid in place? Ask your teacher, or read in the books, the purpose of this.
4. Do all the spore vases stand straight up, or do some bend over?
5. Do you think the silken cap falls off of itself after a while? Can you find any capsules where the cap or veil and the lid have fallen off? See if you can shake any dust out of such a spore vase. What do you think this dust is? Ask your teacher, or read in the books, about moss spores and what happens if they find a damp place in which to grow.
6. Hunt among the moss for some stems that have pretty, yellowish, starlike cups at their tips. How does the inside of one of these cups look? Ask the teacher to tell you what grows in this cup. Look down the stem and see if you can find last year's cup. The cup of two years ago? Measured by these cups how old do you think this moss stem is?
7. Select some stems of moss, both those that bear the fruit and those that bear the cups. After they are dried describe how the leaves look. Examine the plant with a lens and note how these leaves are folded and twisted. Do the leaves stand out from the stem or lie close to it? Is this action of the leaves of any use to the plant in keeping the water from evaporating? How do the star-cups look when dry?
8. Place these dried stems in a glass of water and describe what happens to the cup. Examine some of the dried moss and the wet moss with a lens, and describe the difference. Of what use to the moss is this power of changing form when damp?
Reference—First Lessons in Plant Life, Atkinson.