from which peculiar families have emanated to perform their functions in the great economy of nature.

I.-ITS FLORA OR PLANT-LIFE.

Glancing first at the VEGETABLE WORLD, we perceive that the great regulators of plant-life are heat, light, and moisture. Such is the order of nature now, and such, we are bound to believe, have been the ordainings of creation from the earliest moment that the vegetable cell was evoked into existence. Under the tropics, both individual exuberance and specific variety attain their maximum intensity; in the temperate zones this intensity gradually declines; while in the arctic regions vegetable life dwarfs and diminishes till it ultimately disappears and gives place to utter sterility. As we start from the equator, each great belt-equatorial, tropical, subtropical, warm-temperate, cold-temperate, subarctic, arctic, and polar*-presents its own distinctive features; and though the zones of the southern hemisphere may differ in genera and species from those of the northern, there is still in the respective stages a sufficient resemblance of growth, colouring, and inflorescence, to prove that, latitude for latitude, the prime governing influence is essentially solar. As with latitude, which is influenced in the main by light and heat, so with height above the level of the ocean—an advance upwards into the rarer regions of the atmosphere being equivalent, in some measure, to an advance northwards or southwards into the colder latitudes

* The equatorial zone extends on both sides of the equator to about 15° of latitude; the tropical from 15° to the tropics; the subtropical from the tropics to 34°; the warmer temperate from 34° to 45°; the colder temperate from 45° to 58°; the subarctic from 58° to the polar circle; the arctic from the polar circle to latitude 72°; and the polar zone from 72° to the poles.

of either pole.* The mountain that has its base waving with the palms and tree-ferns of India, may have its sides clothed with the oaks and pines of Europe, its higher cliffs with the dwarf-willows and mosses of Nova Zembla, while its snowy peaks are as void of life as the ice-bound shores of the arctic circle. Besides these conditions, there are others of site, or locality, or habitat-conditions which require that the weeds of the ocean should differ from the plants of the marsh, the plants of the marsh from the herbage of the open plain, and the verdure of the plain distinct from that of the mountain forest. Nay more: there are some tribes that will flourish only in rich organic mould, others that prefer the shingly surface of the arid desert; some that exist only on calcareous soils, and others unknown beyond the limits of the salt marsh. Wherever the prime conditions of heat, light, and moisture are present, there the vegetable germ manifests itself—here incrusting the naked rock, there mantling the surface of the stagnant pool-now rooting itself in the decay of its own kind, and at times finding a habitat even in the tissues of the animal structure. More than this: every climatic influence, however faint, leaves its impress on vegetable life. A thicker layer is added to the concentric growth of the timber-tree during a genial than during an ungenial summer; the southern slopes of a hill are more verdant and flowery than those of its northern side; some plants luxuriate in the sea-breeze which would be death to others; and the leafiest side of a tree is ever that which is most accessible to the open sunshine. Again: plants that grow in localities marked by sudden extremes of heat and cold are always more variable in stature, habit, and foliage, than those which flourish under the steadier influences of a genial

*The capacity of the atmosphere for heat decreases with its density, and this density decreases from the level of the ocean upwards.

climate; and thus we can judge of the climate of a newlydiscovered country, as well as of the conditions that prevailed and affected plant-life during the deposition of a rock-formation, which took place thousands of ages ago. Still further, and apparently altogether independent of climate certain families are restricted to certain regions, beyond which, and under the present arrangements of sea and land, they naturally never pass; and thus it is that the Cape of Good Hope rejoices in its pelargoniums and geraniums; China in its teas and camelias; Australia in its eucalypti and casuarina; the Spanish peninsula in its ever-green oaks; and the pampas of South America in their gigantic thistles and clover, to the almost total exclusion of other species. Descending from family regions to the narrower provinces of genera and species, we find some limited to a single valley, to a solitary island, or, it may be, to some particular mountain-slope which, as far as science can perceive, enjoys no external influence that is not equally shared by the other slopes that surround it.

Beyond all these distinctions there is the difference of KIND-a difference for which science can assign no reason, save that it has pleased the Creator so to create them. Why, for instance, does the moss differ from the rush, the rush from the reed, the reed from the willow, the willow from the birch, the birch from the pine, or the pine from the palm? The oak and the ash grow side by side in the same forest, and yet they are, in the language of naturalists, specifically and generically distinct; the daisy and wild. clover spring from the same soil, and interweave their rootlets to form the same turf, and yet they have no feature or quality in common. That these are facts, the eye of the passing observer may readily perceive; the reason why, man may never know. It is of little avail to talk of the plasticity of the vegetable organism under the force of

external conditions, or to tell us that under these influences the one form is but a modification and development of the other. Even could we establish this fact, and determine the order of its occurrence, it would be no solution of the great primal question of diversity, seeing that plant-life is altogether passive, and that external conditions are of themselves utterly impotent without a higher power to sustain, and an intellect to direct and control, the course of their operations. And, after all, it is less the mere matter of diversity than the plan which connects this diversity into one harmonious system; less the apparent order which may be learned than the reason thereof, to which human knowledge may never attain. God has thought fit so to evoke the vegetable kingdom-to invest His works with variety and complexity; and to unravel this complexity, to arrange these various plants according to their kind and character, to classify them, in accordance with the divine design, into species and genera and orders, and to learn their functions and relations, is the task of the student of Nature. Proceeding upon this plan, the botanist arranges plants according to the complexity of their organs, attempting to separate the simpler from the more highly organised, and these again one from another according to certain dissimilarities and differences of form and function. His aim is to discover the creative idea that pervades the vegetable kingdom; and the nearer he approaches that conception, the more intelligible and permanent his so-called "systems" of arrangenient.

In attempting this arrangement-numerous, varied, and complex as vegetable life may at first sight appear-the botanist has happily a few great fixed principles in nature to guide him. Type and Order run unswervingly throughout the whole; and though the Creator might easily have constructed each species after its own type, and rendered

plants as varied in their individual forms as they are numerically abundant, yet He has thought fit to restrict Himself, as it were, to a few types and models, and, humanly speaking, like a skilful inventor, to produce an almost endless variety from the co-adaptation of a few simple elements, and complexity of design by the elimination of a few primal patterns. As innumerable hues can be produced from a few primitive colours, as endless strains of music flow from the touches of a few simple chords, or as the ideas of all times and nations can be expressed by the combinations of some twenty or thirty letter-sounds; so in the structure of plants and animals every variety of form, every conceivable adaptation of structure, proceeds from the modification of a few elementary forms and types in nature. Without this uniformity of plan and design, the study of nature by man's limited faculties would have been impossible. Bewildered with variety without design, and lost in complexity without order, the human intellect could never have arrived at any true conception of Nature or of Nature's laws; could never have woven those chains of reason wherewith it may be said to have linked earth to heaven, and affiliated the created to the uncreated Creator. But inasmuch as God is a God of law and of order, and clearly meant those laws and orders to be intelligible to our limited comprehensions, so He has considerately narrowed the bounds of creative design, and made creation a theme at once fitted to exercise our reason, and to draw forth our reverence and love. In studying the vegetable world, therefore, the botanist finds that every diversity of form and structure proceeds from the elimination of a simple CELL, and that this cell-growth lies at the basis of all vegetable development. He also finds that the primary structural form into which it is developed is a LEAF or leaf-like organ; and that this leaf-like organ manifests itself variously-rising from a