Through Magic Glasses and Other Lectures Part 4

"Now there are many dark, dank places in the world where plants cannot get enough sunlight and air to make green colouring matter and manufacture their own food. And so it comes to pa.s.s that a certain cla.s.s of plants have found another way of living, by taking their food ready made from other decaying plants and animals, and so avoiding the necessity of manufacturing it for themselves. These plants can live hidden away in dark cellars and damp cupboards, in drains and pipes where no light ever enters, under a thick covering of dead leaves in the forest, under fallen trunks and mossy stones; in fact, wherever decaying matter, whether of plant or animal, can be found for them to feed upon.

"It is to this cla.s.s, called _fungi_, which includes all mushrooms and moulds, mildews, s.m.u.ts, and ferments, that the mushroom belongs which we found yesterday making the fairy rings. And, in truth, we were not so far wrong when we called them pixies or imps, for many of them are indeed imps of mischief, which play sorry pranks in our stores at home and in the fields and forest abroad. They grow on our damp bread, or cheese, or pickles; they destroy fruit and corn, hop and vine, and even take the life of insects and other animals. Yet, on the other hand, they are useful in clearing out unhealthy nooks and corners, and purifying the air; and they can be made to do good work by those who know how to use them; for without ferments we could have neither wine, beer, nor vinegar, nor even the yeast which lightens our bread.

"I am going to-day to introduce you to this large vagabond cla.s.s of plants, that we may see how they live, grow, and spread, what good and bad work they do, and how they do it. And before we come to the mushrooms, which you know so well, we must look at the smaller forms, which do all their work above ground, so that we can observe them. For the _fungi_ are to be found almost everywhere. The film growing over manure-heaps, the yeast plant, the wine fungus, and the vinegar plant; the moulds and mildews covering our cellar-walls and cupboards, or growing on decayed leaves and wood, on stale fruit, bread, or jam, or making black spots on the leaves of the rose, the hop, or the vine; the potato fungus, eating into the potato in the dark ground and producing disease; the s.m.u.t filling the grains of wheat and oats with disease, the ergot feeding on the rye, the rust which destroys beetroot, the rank toadstools and puffb.a.l.l.s, the mushroom we eat, and the truffles which form even their fruit underground,--all these are _fungi_, or lowly plants which have given up making their own food in the sunlight, and take it ready made from the dung, the decaying mould, the root, the leaf, the fruit, or the germ on which they grow. Lastly, the diseases which kill the silkworm and the common house-fly, and even some of the worst skin diseases in man, are caused by minute plants of this cla.s.s feeding upon their hosts."

[Ill.u.s.tration: Fig. 22.

Three forms of vegetable mould magnified.

1, _Mucor Mucedo_. 2, _Aspergillus glaucus_. 3, _Penicillium glauc.u.m_.]

"In fact, the _fungi_ are so widely spread over all things living and dead, that there is scarcely anything free from them in one shape or another. The minute spores, now of one kind, now of another, float in the air, and settling down wherever they find suitable food, have nothing more to do than to feed, fatten, and increase, which they do with wonderful rapidity. Let us take as an example one of the moulds which covers damp leaves, and even the paste and jam in our cupboard. I have some here growing upon a basin of paste, and you see it forms a kind of dense white fur all over the surface, with here and there a bluish-green tinge upon it. This white fur is the common mould, _Mucor Mucedo_ (1, Fig. 22), and the green mould happens in this case to be another mould, _Penicillium glauc.u.m_ (3, Fig. 22); but I must warn you that these minute moulds look very much alike until you examine them under the microscope, and though they are called white, blue, or green moulds, yet any one of them may be coloured at different times of its growth. Another very common and beautiful mould, _Aspergillus glaucus_ (2, Fig. 22), often grows with Mucor on the top of jam.

"All these plants begin with a spore or minute colourless cell of living matter (_s_, Fig. 23), which spends its energy in sending out tubes in all directions into the leaves, fruit, or paste on which it feeds. The living matter, flowing now this way now that, lays down the walls of its tubes as it flows, and by and by, here and there, a tube, instead of working into the paste, grows upwards into the air and swells at the tip into a colourless ball in which a number of minute seed-like bodies called spores are formed. The ball bursts, the spores fall out, and each one begins to form fresh tubes, and so little by little the mould grows denser and thicker by new plants starting in all directions.

"Under the first microscope you will see a slide showing the tubes which spread through the paste, and which are called the _mycelium_ (_m_, Fig.

23), and amongst it are three upright tubes, one just starting _a_, another with the fruit ball forming _b_, and a third _c_, which is bursting and throwing out the spores. The _Aspergillus_ and the _Penicillium_ differ from the _Mucor_ in having their spores naked and not enclosed in a spore-case. In _Penicillium_ they grow like the beads of a necklace one above the other on the top of the upright tube, and can very easily be separated (see Fig. 22); while _Aspergillus_, a most lovely silvery mould, is more complicated in the growth of its spores, for it bears them on many rows branching out from the top of the tube like the rays of a star."

[Ill.u.s.tration: Fig. 23.

_Mucor Mucedo_, greatly magnified. (After Sachs and Brefeld.)

_m_, Mycelium, or tangle of threads. _a_, _b_, _c_, Upright tubes in different stages. _c_, Spore-case bursting and sending out spores. _s_, 1, 2, 3, A growing spore, in different stages, starting a new mycelium.]

"I want you to look at each of these moulds carefully under the microscope, for few people who hastily sc.r.a.pe a mould away, vexed to find it on food or damp clothing, have any idea what a delicate and beautiful structure lies under their hand. These moulds live on decaying matter, but many of the mildews, rusts, and other kinds of fungus, prey upon living plants such as the _s.m.u.t_ of oats (_Ustilago carbo_), and the _bunt_ (_Tilletia caria_) which eats away the inside of the grains of wheat, while another fungus attacks its leaves. There is scarcely a tree or herb which has not one fungus to prey upon it, and many have several, as, for example, the common lime-tree, which is infested by seventy-four different fungi, and the oak by no less than 200.

"So these colourless food-taking plants prey upon their neighbours, while they take their oxygen for breathing from air. The 'ferments,'

however, which live _inside_ plants or fluids, take even their oxygen for breathing from their hosts.

"If you go into the garden in summer and pluck an overripe gooseberry, which is bursting like this one I have here, you will probably find that the pulp looks unhealthy and rotten near the split, and the gooseberry will taste tart and disagreeable. This is because a small fungus has grown inside, and worked a change in the juice of the fruit. At first this fungus spread its tubes outside and merely _fed_ upon the fruit, using oxygen from the air in breathing; but by and by the skin gave way, and the fungus crept inside the gooseberry where it could no longer get any fresh air. In this dilemma it was forced to break up the sugar in the fruit and take the oxygen out of it, leaving behind only alcohol and carbonic acid which give the fermented taste to the fruit.

"So the fungus-imp feeds and grows in nature, and when man gets hold of it he forces it to do the same work for a useful purpose, for the grape-fungus grows in the vats in which grapes are crushed and kept away from air, and tearing up the sugar, leaves alcohol behind in the grape-juice, which in this way becomes wine. So, too, the yeast-fungus grows in the malt and hop liquor, turning it into beer; its spores floating in the fluid and increasing at a marvellous rate, as any housewife knows who, getting yeast for her bread, tries to keep it in a corked bottle.

"The yeast plant has never been found wild. It is only known as a cultivated plant, growing on prepared liquor. The brewer has to sow it by taking some yeast from other beer, or by leaving the liquor exposed to air in which yeast spores are floating; or it will sow itself in the same way in a mixture of water, hops, sugar, and salt, to which a handful of flour is added. It increases at a marvellous rate, one cell budding out of another, while from time to time the living matter in a cell will break up into four parts instead of two, and so four new cells will start and bud. A drop of yeast will very soon cover a gla.s.s slide with this tiny plant, as you will see under the second microscope, where they are now at work (Fig. 24)."

[Ill.u.s.tration: Fig. 24.

Yeast cells growing under the microscope. _a_, Single cells. _b_, Two cells forming by division. _c_, A group of cells where division is going on in all directions.]

"But perhaps the most curious of all the minute fungi are those which grow inside insects and destroy them. At this time of year you may often see a dead fly sticking to the window-pane with a cloudy white ring round it; this poor fly has been killed by a little fungus called _Empusa muscae_. A spore from a former plant has fallen perhaps on the window-pane, or some other spot over which the fly has crawled, and being sticky has fixed itself under the fly's body. Once settled on a favourable spot it sends out a tube, and piercing the skin of the fly, begins to grow rapidly inside. There it forms little round cells one after the other, something like the yeast-cells, till it fills the whole body, feeding on its juices; then each cell sends a tube, like the upright tubes of the _Mucor_ (Fig. 23) out again through the fly's skin, and this tube bursts at the end, and so new spores are set free. It is these tubes, and the spores thrown from them, which you see forming a kind of halo round the dead fly as it clings to the pane. Other fungi in the same way kill the silkworm and the caterpillars of the cabbage b.u.t.terfly. Nor is it only the lower animals which suffer. When we once realise that fungus spores are floating everywhere in the air, we can understand how the terrible microscopic fungi called _bacteria_ will settle on an open wound and cause it to fester if it is not properly dressed.

"Thus we see that these minute fungi are almost everywhere. The larger ones, on the contrary, are confined to the fields and forests, damp walls and hollow trees; or wherever rotting wood, leaves, or manure provide them with sufficient nourishment. Few people have any clear ideas about the growth of a mushroom, except that the part we pick springs up in a single night. The real fact is, that a whole mushroom plant is nothing more than a gigantic mould or mildew, only that it is formed of many different shaped cells, and spreads its tubes _underground_ or through the trunks of trees instead of in paste or jam, as in the case of the mould."

[Ill.u.s.tration: Fig. 25.

Early stages of the mushroom. (After Sachs.)

_m_, Mycelium. _b1-3_, Mushroom buds of different ages. _b4_, b.u.t.ton mushroom. _g_, Gills forming inside before lower attachment of the cap gives way at _v_.]

"The part which we gather and call a mushroom, a toadstool, or a puffball is only the fruit, answering to the round b.a.l.l.s of the mould.

The rest of the plant is a thick network of tubes, which you will see under the third microscope. These tubes spread underground and suck in decayed matter from the earth; they form the _mycelium_ (_m_, Fig. 25) such as we found in the mould. The mushroom-growers call it 'mushroom sp.a.w.n' because they use it to spread over the ground for new crops. Out of these underground tubes there springs up from time to time a swollen round body no bigger at first than a mustard seed (_b1_, Fig. 25). As it increases in size it comes above ground and grows into the mushroom or spore-case, answering to the round b.a.l.l.s which contain the spores of the mould. At first this swollen body is egg-shaped, the top half being largest and broadest, and the fruit is then called a 'b.u.t.ton-mushroom'

_b4_. Inside this ball are now formed a series of folds made of long cells, some of which are soon to bear spores just as the tubes in the mould did, and while these are forming and ripening, a way out is preparing for them. For as the mushroom grows, the skin of the lower part of the ball (_v_, _b4_) is stretched more and more, till it can bear the strain no longer and breaks away from the stalk; then the ball expands into an umbrella, leaving a piece of torn skin, called the veil (_v_, Fig. 26), clinging to the stalk."

[Ill.u.s.tration: Fig. 26.

Later stages of the mushroom. (After Gautier.)

1, b.u.t.ton mushroom stage. _c_, Cap. _v_, Veil. _g_, Gills.

2, Full-grown mushroom, showing veil v after the cap is quite free, and the gills or lamellae _g_, of which the structure is shown in Fig. 27.]

"All this happens in a single night, and the mushroom is complete, with a stem up the centre and a broad cap, under which are the folds which bear the spores. Thus much you can see for yourselves at any time by finding a place where mushrooms grow and looking for them late at night and early in the morning so as to get the different stages. But now we must turn to the microscope, and cutting off one of the folds, which branch out under the cap like the spokes of a wheel, take a slice across it (1, Fig. 27) and examine."

[Ill.u.s.tration: Fig. 27.

1, One of the gills or lamellae of the mushroom slightly magnified, showing the cells round the edge. _c_, Cells which do not bear spores.

_fc_, Fertile cells. 2, A piece of the edge of the same powerfully magnified, showing how the spores _s_ grow out of the tip of the fertile cells _fc_.]

"First, under a moderate power, you will see the cells forming the centre of the fold and the layer of long cells (_c_ and _fc_) which are closely packed all round the edge. Some of these cells project beyond the others, and it is they which bear the spores. We see this plainly under a very strong power when you can distinguish the sterile cells _c_ and the fertile cells _fc_ projecting beyond them, and each bearing four spore-cells _s_ on four little horns at its tip.

"These spores fall off very easily, and you can make a pretty experiment by cutting off a large mushroom head in the early morning and putting it flat upon a piece of paper. In a few hours, if you lift it very carefully, you will find a number of dark lines on the paper, radiating from a centre like the spokes of a wheel, each line being composed of the spores which have fallen from a fold as it grew ripe. They are so minute that many thousands would be required to make up the size of the head of an ordinary pin, yet if you gather the spores of the several kinds of mushroom, and examine them under a strong microscope, you will find that even these specks of matter a.s.sume different shapes in the various species.

"You will be astonished too at the immense number of spores contained in a single mushroom head, for they are reckoned by millions; and when we remember that each one of these is the starting point of a new plant, it reminds us forcibly of the wholesale destruction of spores and seeds which must go on in nature, otherwise the mushrooms and their companions would soon cover every inch of the whole world.

"As it is, they are spread abroad by the wind, and wherever they escape destruction they lie waiting in every nook and corner till, after the hot summer, showers of rain hasten the decay of plants and leaves, and then the mushrooms, toadstools, and puffb.a.l.l.s, grow at an astounding pace. If you go into the woods at this season you may see the enormous deep-red liver fungus (_Fistulina hepatica_) growing on the oak-trees, in patches which weigh from twenty to thirty pounds; or the glorious orange-coloured fungus (_Tremella mesenterica_) growing on bare sticks or stumps of furze; or among dead leaves you may easily chance on the little caps of the crimson, scarlet, snowy white, or orange-coloured fungi which grow in almost every wood. From white to yellow, yellow to red, red to crimson and purple black, there is hardly any colour you may not find among this gaily-decked tribe; and who can wonder that the small bright-coloured caps have been supposed to cover tiny imps or elves, who used the large mushrooms to serve for their stools and tables?

"There they work, thrusting their tubes into twigs and dead branches, rotting trunks and decaying leaves, breaking up the hard wood and tough fibres, and building them up into delicate cells, which by and by die and leave their remains as food for the early growing plants in the spring. So we see that in their way the mushrooms and toadstools are good imps after all, for the tender shoot of a young seedling plant could take no food out of a hard tree-trunk, but it finds the work done for it by the fungus, the rich nourishment being spread around its young roots ready to be imbibed.

"To find our fairy-ring mushrooms, however, we must leave the wood and go out into the open country, especially on the downs and moors and rough meadows, where the land is poor and the gra.s.s coa.r.s.e and spare.

There grow the nourishing kinds, most of which we can eat, and among these is the delicate little champignon or 'Scotch-bonnet' mushroom, _Marasmius Oreades_,[1] which makes the fairy-rings. When a spore of this mushroom begins to grow, it sucks up vegetable food out of the earth and spreads its tubes underground, in all directions from the centre, so that the mycelium forms a round patch like a thick underground circular cobweb. In the summer and autumn, when the weather is suitable, it sends up its delicate pale-brown caps, which we may gather and eat without stopping the growth of the plant.

[1] Shown in initial letter of this chapter.

"This goes on year after year underground, new tubes always travelling outwards till the circle widens and widens like the rings of water on a pond, only that it spreads very slowly, making a new ring each year, which is often composed of a ma.s.s of tubes as much as a foot thick in the ground, and the tender tubes in the centre die away as the new ones form a larger hoop outside.

"But all this is below ground; where then are our fairy rings? Here is the secret. The tubes, as we have seen, take up food from the earth and build it up into delicate cells, which decay very soon, and as they die make a rich manure at the roots of the gra.s.s. So each season the cells of last year's ring make a rich feeding-ground for the young gra.s.s, which springs up fresh and green in a fairy ring, while _outside_ this emerald circle the mushroom tubes are still growing and increasing underneath the gra.s.s, so that next year, when the present ring is no longer richly fed, and has become faded and brown like the rest of the moor, another ring will spring up outside it, feeding on the prepared food below."

"In bad seasons, though the tubes go on spreading and growing below, the mushroom fruit does not always appear above ground. The plant will only fruit freely when the ground has been well warmed by the summer sun, followed by damp weather to moisten it. This gives us a rich crop of mushrooms all over the country, and it is then you can best see the ring of fairy mushrooms circling outside the green hoop of fresh gra.s.s. In any case the early morning is the time to find them; it is only in very sheltered spots that they sometimes last through the day, or come up towards evening, as I found them last night on the warm damp side of the dell.

"This is the true history of fairy rings, and now go and look for yourselves under the microscopes. Under the first three you will find the three different kinds of mould of our diagram (Fig. 22). Under the fourth the spores of the mould are shown in their first growth putting out the tubes to form the mycelium. The fifth shows the mould itself with its fruit-bearing tubes, one of which is bursting. Under the sixth the yeast plant is growing; the seventh shows a slice of one of the folds of the common mushroom with its spore-bearing horns; and under the eighth I have put some spores from different mushrooms, that you may see what curious shapes they a.s.sume.

"Lastly, let me remind you, now that the autumn and winter are coming, that you will find mushrooms, toadstools, puffb.a.l.l.s, and moulds in plenty wherever you go. Learn to know them, their different shapes and colours, and above all the special nooks each one chooses for its home.

Look around in the fields and woods and take note of the decaying plants and trees, leaves and bark, insects and dead remains of all kinds. Upon each of these you will find some fungus growing, breaking up their tissues and devouring the nourishing food they provide. Watch these spots, and note the soft spongy soil which will collect there, and then when the spring comes, notice what tender plants flourish upon these rich feeding grounds. You will thus see for yourselves that the fungi, though they feed upon others, are not entirely mischief-workers, but also perform their part in the general work of life."

CHAPTER IV