The process of artificially producing mushroom spores is a very simple one, and may be easily followed. You have only to collect a quantity of horse-droppings, mingle with them some common road sand, place them under cover, see that they are well beaten down in order to prevent over-heating--turning them occasionally for the same purpose--and in due time they will generate sufficient spores for a dozen mushroom beds of the ordinary size. The reason for their appearance is the same as that governing truffle spores--they come whenever conditions favor, that is, whenever the soil is chemically balanced for their development and growth. In other words, they come because it is just as impossible for them not to come, in their proper environing conditions, as it is for the earth, in its present cosmical relations, not to respond to its axial rotation. "Let the earth bring forth" is just as much an outspoken law of nature, and one as inexorably obeyed, as that unerring force of gravity which led Leverrier, in the faith of his inductions, to indicate the precise point in the heavens where the far-off planet, now bearing his name, might be seen by the required telescope.
Dr. Cooke, quoting Mr. Cuthill's directions for producing mushroom spores, says: "These little collections of horse-droppings and road sand, if kept dry in shed, hole, or corner, under cover, will, in a short time, generate plenty of spawn, and will be ready to spread on the surface of the bed in early autumn." The collections should, of course, be made in the early summer. But it is no part of our object to indicate, in this connection, the process of truffle or mushroom culture. We merely refer to the methods to show that the vital units, or germinal principles of life, in the case of fungi, are just as dependent on "conditions" for their development, as were the primordial germs of the gigantic cryptogams of the carboniferous era. These primordial germs, or the ZRA of the Bible genesis, must have preceded the first fungous growth, as they preceded the first spore-bearing cryptogam.
M. Gasparin, in his report on the production of truffles, made to the great "Paris Exposition" of 1855, refers to the "natural truffle-grounds at Vaucluse," where the "common oak produces truffles like the evergreen oak;" although, in other localities, owing no doubt to the different conditions of the soil, those gathered at the base of the one species of oak differ very materially from those gathered at the base of the other. All these experimental results, and many others we might give in connection with the culture of edible fungi, point to the conditions of the soil, produced by natural rather than artificial means, as all-essential for the propagation of fungus spores, as well as their development into full-sized plants. The cultivation of other and minuter fungi, for scientific purposes, need not be referred to in this connection. The same general observations will be found to apply in the case of all the experiments tried, although some very curious and remarkable modifications occur where pseudospores are to be found in the micelium of different plants. Nearly all these fungi have their own parasites, originating undoubtedly in the diseased conditions of the plant from which they derive their nutriment. Indeed, all fungi, whether parasitic or non-parasitic, have their origin, more or less definitely occurring, in decay. It is no more true that death is a necessity of life, than that life is an equal necessity of death. As out of the dead past springs the eternally living present, so from the "muddy vesture of decay" spring all the marvellous powers of reproduction with which nature was endowed from the beginning.
But it is unnecessary to dwell longer on the spores of fungi. As with the seeds of plants and trees, these spores never had an existence, and never could have had one, before the first independent fungus appeared to produce them. The fungus before the spore is the inevitable induction. No distinction between necessary and contingent truth can ever take a stronger hold than this on the human mind. Whence, then, the first fungus? or whence, rather, all those colonies, families, orders, divisions, and countless distinct individuals, extant everywhere, in the mycological world? The answer we shall give will be anticipated from what we have already so confidently affirmed. Life comes from Life, as spirit comes from God. And when "the spirit of God" moved upon the face of the depths--upon the face of all the earth--at whatever stage in the progress of our planet, from its original form to its present myriad-thronged condition of life, that transcendent event occurred, Nature, as we half-idolatrously worship her, received her first baptism of life, and her solemn consecration as "the vicar of God." No wonder, then, that at that ecstatic moment, when the ineffably bright mantle, fringed with "the white radiance of eternity," fell upon her, "the morning stars sang together and all the sons of God shouted for joy." And nature has been true to both her baptism and her consecration. She claims no worship, no adoration, no idolatrous homage from man, but continually sends up her eternal chant and choral anthem of praise to the great Giver of life. Every flower of the field, every blade of grass, every stream that mirrors the heavens above her, every mountain top from which she points an index finger, every breeze in which she whispers, and every cataract in which she speaks, all proclaim the power, the wisdom, the goodness of God--the source of all life in the universe, from the minutest spore to all-inventive, soul-endowed man.
Chapter V.
Plant Migration and Interglacial Periods.
Among the leading propositions laid down by Arthur Renfrey, Esq., F.R.S. etc., etc., in the able article prepared by him for "The Physical Atlas of Natural Phenomena," by Alexander Keith Johnston, Edinburg Edition, 1856, on "The Geographical Distribution of the most Important Plants Yielding Food," are the following:--
1. "The primary condition of the existence of any species of plant, is its absolute creation, of which we know nothing.
2. "But we assume each species to have been created but once in time and in place, and that its present diffusion is the result of its own law of reproduction under the favorable or restrictive influences of laws external to it.[[14]]
3. "The most important of external laws are those relating to climate, since any species can flourish only within narrower or wider, but always fixed limits, of temperature, humidity etc.,