In some countries, particularly in the tropics, there are (as well as ferns like ours) very large ferns with tall, strong, upright stems, and crowns of large spreading leaves. Such ferns you can see in Plate III., and they are called tree ferns. Notice how thick the stem is, and how large the leaves are compared with it, while the trunk seems to be all rough and hairy, which is due to the jagged bases of the old leaves which have fallen away. Yet even the tree ferns are easily recognised as belonging to the fern family.
Let us examine ferns in order to find out what are the points about them which are specially characteristic for their family, and which help us to separate them from the other plants.
1. We find that the fern body is clearly marked out into roots, stem, and leaves, but there appear to be neither flowers nor cones.
2. The stem and roots have definite “water-pipe” cells, as you can see if you examine a thin slice with your magnifying-glass, but there are never rings of wood formed year by year, as in the higher families. The stems are frequently short and stumpy, and often run underground. They are usually covered by the rough leaf-bases of old leaves and by dry scales.
3. The leaves are generally few in number, often only three or four, but they are highly compound, and are split up into very many side leaflets. They are generally thin and delicate. When they are young they are rolled up in the bud in a close coil (see fig. 127), and as they unfold they bend back. This way of coiling up is quite a special character of ferns. The buds are generally covered with flaky, shining scales, which stick all over the young leaf-stalk.
Fig. 127. Young leaf of a Fern rolled in a close coil.
4. You have never seen a fern with flowers or seeds, yet there are always plenty of new ferns every year. How are the young ones formed? For a long time botanists did not know, so that people thought there was some magic about it, but now we know the whole story, and it is a very interesting one.