and to cheer and instruct many a heavy-hearted wanderer through the wilderness of earth. And busy little missionaries of light and beauty have they been. What spot of earth have they not struggled to cover with their verdure and their smiles? Along the borders of the Sahara, where restless waves of sand and the heated winds of the simoon prevent all animal life, are found broad and deep coast-lines of verdure, and flowers and plants and the graceful palm stand eagerly vying with each other to dispute every inch of soil with the howling storms of the desert; and occasionally a seed, taking advantage of the gale, leaps from its parent stem, and, riding upon the storm, is carried for miles to some little island-home in the sand, where, taking root, it soon achieves a victory, and beautiful verdure springs up to hide the former barrenness. Others have found their way into regions of perpetual ice; and Captain Richardson speaks of plants and small flowers which bloomed so near to the Polar regions that gloomy piles of ice lay on the ground as their companions during the entire year. Some, with a remarkable fitness to all the peculiarities of the countries whither they wander, have been found in Iceland, running their delicate roots into the hot waters of the boiling springs, and thence drawing nourishment which. permits them to continue from year to year putting forth blossoms and bearing seed in continuance of a life so welcome and so singular. Farther south, and near to Naples, is the Grotto del Cane,* out of which issues a pestiferous breath

* Called thus the "cave of the dog"-because of the fact that a dog on entering sank down helpless, and thus led to the discovery of the deadly air which settles near the ground.

that permits no life, not even of an insect. Yet I have seen little leaves and mosses and tiny blossoms as if they condescended to cast a veil of beauty over the dark rocks of that dismal cave, because they could live where all else died. Sulphurous fumes of the lake not far from this cave penetrate the mud on its margin, and bubble up in a gas which has rapidly tarnished the silver coin I have placed on the shore near its waters; and yet even there, amid those volcanic vapors, as on the island of Ischia not far off, can be seen mosses and ferns beautiful and graceful, bending before those breezes which, as they pass over them, gently shake out from their bright petals the poisonous air they endure that they may line with life and verdure the shore which suggested to the Greek poets the idea of the infernal lake. Now let us pass to the east, up the rugged heights of Vesuvius, and over the crumbling crags of lava, which have left a wild desolation triumphing over the soil, and covering the land for miles with the ragged mantle of volcanic fury. Even here we shall find that some little modest plant has preceded us, and, springing from a winged seed wafted up in the wind or carried on the dress of some traveller, has dared to plant its roots and spread out its mottled covering as a moss or lichen, or to erect its peaceful standard upon some rock, and, drinking in the moisture of the passing clouds, has set up for itself in that desolate region. And there it will grow, and, when its joyous mission is over, will droop anddie; and after its death, in obedience to a wonderful chemical law, its little microscopic roots (or basis, if a lichen) will send forth an acid which shall eat into the desolate rock until it

shall form both cells and soil, that the future plant may crown that rock with a deeper and stronger verdure than before. Thus will they work, until in time that cragged mass of lava shall yield before its quiet conquerors, and, crumbling into dust, become the fit soil for the growth of trees and forests. Thus in many regions the sun and showers alone combine with plants to reduce large rocks to soil.

Where there is life at all on the earth, it seems first to have been vegetable life. Little plants, like pioneers, have gone forth to prepare the way, and animal life has followed.

But if we will follow all vegetation, we must prepare to leave the surface of the land and wander far beneath that surface, into the depths of caves and fissures and mines. Clothing even the stalactites of caverns I have found vegetation, which under the microscope exhibited all the beauteous branching forms and roots of plants which grow beneath the light of day. And then they crowd into life between. the rocks and rubbish of mines, apparently satisfied to live where no ray of light has ever penetrated.

There is yet another region, whose vegetation is as varied and mysterious in its life and beauty as that which holds its empire on the land. This region is that of the waters, where vegetation assumes a form and character modified by the nature of the new world in which it appears; but in its necessities, its tenacity of life, its beauty of form and color, and its wandering travels, it is still the same. Some sea-plants are so similar to those of the land that in branch and color we immediately see a mutual likeness. Others take upon them the

forms of sea-mosses, sponges, and lichens, and depart so widely from the nature of plants that we leave them to be noticed. in other scientific works than those on botany.

How have plants travelled from one region to another, especially where their delicate forms have preceded man, and been found growing on mountain-tops never before trodden by human steps? There is a natural tendency in flower-bearing plants to diffuse themselves over the earth; but this is effected chiefly by means of the seeds, aided by the dust of flowers, called the pollen. The history of the pollen is as full of mystery and wonder as is the movement of a distant planet or satellite. Every flower contains this dust, without which the plant will fail to produce a healthful seed or fruit. In some the pollen can be gathered upon the finger when introduced into the open flower. In others it is so minute as to be invisible. A greater contrast exists between the seeds, which range from five pounds, as in the cocoanut, to the dust-like form of some varieties of the mushroom and the so called puffball. When the latter bursts, the seeds escape in a small cloud and are carried on the lightest breeze for many miles. Other plants and lichens of the lowest order send forth particles of seed-dust so small as to be invisible to the naked eye, which, floating on the air, enter the smallest crack, and have settled even in the lungs of birds and men and there made for themselves a strange soil, to commence a growth which has either been destroyed by some effort of nature or has injured the texture of the lungs itself. A grain of fine dustseed has been known to lodge in the joints of the wasp in the

West Indies, and, finding room for its tiny roots, has there spread forth its branches, and thus been carried from place to place on the back of the insect. Some larger seeds, unable to travel through the air without aid, are provided with various forms of wings and fringes, and, thus prepared, have been caught up by the wind and have travelled many miles uninjured. Linnæus supposes that a plant (Erigeron Canadense) which suddenly appeared in England, never before known except in Canada, grew from a seed which had crossed the Atlantic through the air. And seeds have sprung up on the southern coast of Spain which had ripened on the northern shores of Africa.

While some flowers produce the pollen which is necessary to its own fruitfulness, others will bear no fruit unless the pollen from others fall upon the pistils of their own flowers. In that little floating particle of pollen-dust resides the mysterious power to produce a seed which shall spring up, and bear leaves, and branches, and flowers, and fruit, which often show the very diseases of the parent tree. Under the microscope each minute particle of dust which forms the pollen of a lily appears precisely like all the other pollen of the same flower; and this form will always be the same for every lily. In one flower the dust is like a ball, having on its surface eight equidistant points, as in the hollyhock; and that form will always be found the same in that flower. In others, as in the fuchsia (lady's ear-drop) and violet, its form is that of an egg with varying compartments. In others, again, the form is triangular, or elongated, or pointed; but in each flower the pollen presents a change