The Swan And Her Crew Part 25

To anyone fond of ferns nothing can be more interesting than a fern-case. Nearly all ferns grow well in them, if they are properly attended to. Whenever the soil becomes dry on the surface, they should be well watered, and this should not be done too often, or it will encourage the growth of mould. The moisture will evaporate and condense on the side of the gla.s.s, and run down again to the earth, so that there is very little waste. The plants thus create an atmosphere of their own, and will thrive in it wonderfully.

[Ill.u.s.tration: WALL RUE. JERSEY FERN. MARSH FERN.]

One day it was so intensely hot that it was impossible to do anything but lie in the shade. The boys had bathed twice, and the deck planks of the yacht were so burning hot that they could with difficulty stand upon them. They sought a shady corner of the paddock, and there underneath a tall hedge and the shade of an oak they lay, and talked, and read. Frank was teasing d.i.c.k with a piece of gra.s.s, and to escape him, d.i.c.k got up and sat on a rail in the hedge which separated them from the next field, which was a corn-field. This quietly gave way, and d.i.c.k rolled into the next field, and lay among the corn quite happy and contented. Suddenly he called out--

"Come and look at this nest in the corn-stalks! It can't be a bird's.

What is it?"

Frank and Jimmy went through the gap and examined it.

[Ill.u.s.tration: HARVEST MOUSE AND NEST.]

"It is the nest of a harvest mouse," said Frank, "and there are half a dozen naked little mice inside."

The harvest mouse is the smallest of British animals. Unlike its relatives, it builds its nest in the stalks of gra.s.s or corn at a little distance from the ground. The nest is globular in shape, made of woven gra.s.s, and has a small entrance like that of a wren's.

[Ill.u.s.tration: MOLE.]

"And here is a mole-trap," said Jimmy, "with a mole in it. What smooth glossy fur it has! It will set whichever way you rub it."

"Yes; and don't you see the use of that. It can run backwards or forwards along its narrow burrows with the greatest ease. It could not do that if the fur had a right and a wrong way."

"Can it see?" asked Jimmy, pointing to the tiny black specks which represented its eyes.

"Oh yes. Not very well, I dare say; but well enough for its own purposes. It can run along its pa.s.sages at a great speed, as people have found out by putting straws at intervals along them, and then startling the mole at one end and watching the straws as they were thrown down."

During the autumn and winter the mole resides in a fortress, often at short distances from the burrow where it nests. This fortress is always placed in a position of safety, and is of a most complex construction.

It is a hillock, containing two or three tiers of galleries with connecting pa.s.sages, and from the central chamber it has pa.s.sages, or rows, extending in different directions.

[Ill.u.s.tration: LADYBIRD AND ITS STAGES.]

The boys returned to their couches in the long gra.s.s in the shade, and Frank was soon too sleepy to tease, but lay on the broad of his back, looking up at the blue sky through the interstices of the oak branches.

d.i.c.k was studying the movements of a ladybird with red back and black spots, which was crawling up a gra.s.s-stem, and wondering how such a pretty creature could eat a green juicy aphis, as it has a habit of doing. Jimmy was turning over the pages of his book, and looking out the plates of flowers, and comparing them with some he had gathered. He was rather bewildered and somewhat discouraged at the immensity of the study he had undertaken. No sooner did he learn the name of a flower than it was driven from his head by that of another, and having attempted to do too much in the beginning, he had got into a pretty state of confusion.

He had given up the idea of keeping pace with naming all the beautiful flowers he had found. He gathered and dried them, and left to the winter evenings the task of arranging and naming them.

"I say," called out Frank, "around my face there are at least seven different kinds of gra.s.ses. Can you name them, Jimmy?--and how many different kinds of gra.s.ses are there?"

"I can name nothing," said Jimmy dolefully, "but I will look it up in my book and tell you. Here it is, but their name seems legion. You must look at them for yourself. The plates are very beautiful, but the quaking gra.s.s, of which there is any quant.i.ty just by your head, is the prettiest."

"They seem as pretty as ferns," said Frank. "I must learn something more about them."

A day or two after this Mr. Meredith said to them, when they had a.s.sembled at his house in the morning:

"Now, boys, from something a little bird has whispered to me, I think you stand in need of a little punishment, and I therefore mean to give you a lesson. You are by far too desultory in your study of natural history. You attempt to do too much, and so you only obtain a superficial knowledge, instead of the thorough and practical one you ought to have. You are trying to reach a goal before you have fairly started from the toe-line. I allude more especially now to botanical matters, because I know most about them, and that is all I can help you in. Therefore you will be kind enough to translate into Latin this Essay which I have written on the Life of a Fern."

"That is anything but a punishment, sir," said Frank, laughing.

The boys set to work with great zest at their novel lesson. I set the English of it out in the next chapter, and I particularly request my young readers to read every word of it.

CHAPTER XXVI.

The Life of a Fern.[1]

[1] For this Chapter I am indebted to my friend Mr. William Whitwell, of Oxford.

One of the most marvellous of "the fairy tales of science" has now to engage our attention for a time. The growth and fertilization of the seeds--more properly called spores--of ferns, present phenomena of remarkable singularity and interest. Growth is advisedly named first, as in the present instance it really does occur before fertilization, which is not the primary event in the life-history of a fern.

But a few words must be devoted to the preliminary question: What is a fern?

The vegetable kingdom is divided into two great provinces, allotted respectively to the flowering and the flowerless tribes. The flowering plants have several distinct and visible organs for the formation and fertilization of their seed, to each of which is a.s.signed a special and necessary office. In the flowerless section, on the contrary, there are none of these visibly separate agencies in reproduction, and what are usually termed the seeds do not show any parts representative of the developed product. In the true seeds, which belong to flowering plants alone, are contained the rudiments of a stem, leaves, and root, but in the spores of the flowerless plants nothing of the kind is found. The spores, again, are microscopic, while the smallest of true seeds can be not only seen but easily picked up. You have, doubtless, met with the peculiar fungus called a puff-ball, and amused yourselves by watching the little clouds of impalpable dust which are shaken from it on the slightest motion. Those fine clouds, not nearly so visible as a film of candle smoke, are composed of innumerable spores, and such are the representatives of seeds in every member of the great section of the flowerless plants.

Now it is peculiar to ferns, that the cases in which these spores are enclosed grow directly from the veins of what is usually called the leaf, but is more correctly termed the frond, and always appear upon the back or at the margin.

Ferns, then, are flowerless plants which bear their spores in cases growing upon the back or margin of the leaves.

In order that the phenomena of growth and fertilization in ferns may be clearly understood, it is necessary to refer to the process as taking place in flowering plants. The tulip is most appropriate for an ill.u.s.tration, inasmuch as its various parts will be recognised with ease.

At the bottom of the blossom is a thick green oval body called the ovary, which afterwards becomes the seed-vessel. At the top, this narrows into a short column, surmounted by a three-cleft k.n.o.b. Between the ovary and the gorgeously painted flower-leaves are six curious organs, termed stamens, consisting each of a long and rather slender stalk, and a head formed somewhat like a hammer.

If the green oval ovary in the centre is cut in two, it will be found divided into three chambers, in one or another of which, not usually in all, will be seen a row of little k.n.o.bs or b.u.t.tons attached to the part.i.tion in the middle. These little b.u.t.tons are ovules, or seed-germs, and the special office of the ovary is to produce these germs, and to contain them until their full development and complete ripening into seeds. But if the k.n.o.bs are left just as they are, unfertilized, they can never become seeds, and the plant will fail to reproduce its kind.

Turn we now to the stamens. Each of their hammer-like heads has two chambers, full of beautiful little grains which are called the pollen.

Each grain is tastefully and delicately marked, and holds a transparent watery fluid, in which a number of extremely small solid particles are floating. What is required for the fertilization of the seed-germs is--that this fluid should be conveyed to and taken up by them. But they are in the centre of the thick green ovary--this in the chambers of the stamens!

A simple arrangement brings all about. At a certain time we may see the black heads of the stamens covered with a fine flour, which adheres to whatever touches them. This flour is made up solely of pollen-grains, escaping in unimaginable numbers from the chambers where they are produced. At the same time the k.n.o.b which crowns the seed-vessel puts forth a thick and gummy ooze. The stamens are just long enough for their heads to rise a little above this k.n.o.b, upon which the pollen, when escaping as I have stated, falls in great quant.i.ty, and is there held fast.

Each grain then begins to swell, and to sprout (as the Rev. J. G. Wood has it) something like potatoes in a cellar. All the sprouts, however, pierce the k.n.o.b, and push downwards until they reach the seed-germs underneath. Each sprout is a tube of extreme minuteness, and when it reaches a germ, attaches itself thereto, and, through the channel so formed, the fluid is drawn out of the pollen-grain and absorbed by the embryo seed. Fertilization is thus effected, and the growth and development of the germ proceeds until it becomes a seed fully able, when planted, to reproduce a tulip.

[Ill.u.s.tration: FERN SPORES.]

In ferns, the spores ripen and are ready for dispersion and partial growth without any process of the kind. But, in truth, fertilization is as necessary to the continuance of ferns as to the perpetuation of other plants. The main difference lies in this: that the means of fertilization, and the real germs of new plants, are produced from the spores after they begin to grow.

When a spore falls upon a proper place for its development, a portion of the outer membrane begins to swell, and a tongue-shaped projection is formed, which becomes a sort of root. The one chamber of the spore gradually subdivides, and becomes two, four, and so on, until for the simple spore we have a tiny leaf-like expansion, now known as the _prothallium_, or representative of a leaf.

Further than this the spore alone has no power to go, and the prothallium is not truly the germ of the future plant. True germs, needing fertilization, are produced upon it, and also the means whereby they can be fertilized. These can be distinguished only by use of the higher microscopic powers. If a portion of the prothallium is examined, it will be found studded with little bladders, containing round semi-transparent bodies of a greenish hue.

There may also be seen, though in fewer numbers, pellucid cells of an entirely different character, consisting apparently only of a fine membrane, forming an angular chamber, shaped in some instances like a lantern of extreme delicacy and elegance. From the top of this chamber a funnel-like shaft descends to a little germ which is situated at the bottom. This germ is the real original of the future plant, and the round bodies in their little cells, just before described, are the means whereby it is to be fertilized and receive energy to develope into the perfect fern.

But how can the needful contact between the germs and the fertilizing bodies be brought about? Observation and experiment supply a strange answer to this question.

The round bodies in the tiny bladders acquire a spiral or sh.e.l.l-like form when they become mature. If a drop of water is then placed in contact with the bladders, their contents will suddenly escape, retaining for a moment the coiled appearance, but quickly lengthening and partially unrolling.

By means of hairs with which they are furnished, and which at once commence a ceaseless jerking motion, they forthwith launch out into the water, and conduct themselves therein more like creatures endowed with conscious life than mere organs of a settled and sedate member of the vegetable kingdom.