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_.,