FIG. 8.

extraordinary form. They are distinguished from roots by the production of leaf-buds. Some are slender, and creep along the ground, as in strawberries. On the other hand, the bulbs of the onion and lily are reckoned stems; and even the potato, whose leaf-buds are familiarly called eyes, belongs rather to the stem than to the root. It is, in fact, a kind of subterranean branch. Stems are divided, according to their mode of growth, into three classes, corresponding exactly to the three classes of plants which are determined by the structure of the seed. In our forest trees, and all those plants already described as dicotyledonous, the stem increases outwards, a new layer of woody matter being deposited every year immediately below the bark. When the trunk of a tree is sawn across, these layers are distinctly visible, and by their number the age of the tree can be exactly ascertained.

Such stems are called exogenous. The stems of monocotyledonous plants, on the other hand, increase inwardly, and are therefore called endogenous. In their case, the oldest and hardest part of the stem is the outside; they have no separable bark, and, generally speaking, no branches. Similar to them in these last respects are the stems of acotyledonous plants, which, altering little in thickness after being once formed, and increasing chiefly by additions to the summit, have received the name of acrogenous.

The leaves of plants play a very important part in carrying out the process of nutrition. Like the stem, they are of various forms, and (what is remarkable enough) a classi fication of plants according to these forms would nearly coincide with the two coincident classifications already referred to. In most exogenous plants, the ribs and veins of the leaves cross each other, so as to form a sort of net

work, while in endogenous plants the veins are more or less parallel, and a variety of this latter form is characteristic of acrogenous plants. Leaves, as well as roots, are provided with little mouths; not, however, at their extremities merely, but over their whole surface. By means of these they extract nourishment from the air, and also exhale moisture, sometimes in such quantities as to affect the climate of a country. Hence the destruction of a forest not unfrequently makes a climate drier than it was before. The value of leaves in purifying the atmosphere, by the absorption and decomposition of carbonic acid gas, has been already noticed. But there is still another function of great importance which these organs perform. The fluids imbibed by the roots are conveyed through the stem to the leaves, in whose living laboratory, acting under the stimulating influence of air and light, they are transformed into those organic compounds on which the plant feeds. Thus prepared, they are then distributed over every part of the organism.

How can we sufficiently admire the wisdom which has endowed a structure apparently so simple, and withal so beautiful, with powers as various and wonderful as they are essential to the welfare of the plant! We examine the organs, and we see the result of their action, but who can tell the real nature of those processes by which the ends of their existence are attained? It was an empty boast of the proud naturalist, which he ordered to be inscribed on his statue "A genius equal to the majesty of nature;" for it has been well remarked, that a single blade of grass was sufficient to confound his pretensions.

QUESTIONS FOR EXAMINATION.

In what respects are plants useful to man? What purpose is served by their beauty? What lesson should we learn from it? How many species of plants are known? What effect does the breathing of animals produce on the surrounding air? How is this effect counteracted? What would happen if it were not counteracted? Of what parts do seeds usually consist? What is the use of the cotyledons, and what becomes of them as the plant grows? From which part of the seed does the root of the plant proceed? Which part sprouts upwards? Explain the words dicotyledonous, monocotyledonous, and acotyle. donous, with examples. Name some plants which are propagated by spores.

What is the influence on germination of moisture? of air? of heat? of light? What are the organs of nutrition in plants? What are the uses of the root! How does it accomodate itself to the soil? Which parts of it imbibe nourishment? In what form must such nourishment be? What is the use of manure? Give examples of peculiarly shaped stems. Classify stems according to their mode of growth. What kind of leaves usually grow on exogenous stems! on endogenous stems? What is the effect of leaves on climate? What pur. poses do they serve in nourishing the plant?

EXCHANGE.

In the earlier stages of society, exchanges were effected by direct giving and taking of commodity for commodity, or, as it is termed, barter; but great and serious difficulties attended this system, difficulties ever more deeply felt as exchanges multiply and become more various: the baker may not want the shoemaker's shoes, if the latter want his bread; but the latter may not want as much bread as equals the value of a pair of shoes, and payment by a half or a third of a pair of shoes is impossible. A medium of exchange, accordingly, is introduced; usually, the precious metals. Exchange, thus facilitated by the adoption of a medium which all are ready to receive, and by which most minute proportions of value may be easily represented, proceeds with vastly increased rapidity.

Exchanges becoming thus continually more frequent and complicated, it is found convenient and advantageous, on the principle of the division of labour, that a class of men should devote themselves to conduct the business of exchange solely, the work of production being left to others. By the introduction of merchants, who do not themselves produce, a greater amount of production is attained, on the whole, than would be possible if all both produced and exchanged without their intervention.

But for facility and frequency of exchange, even at home, rapidity, and ease, and safety of communication are indispensable; good roads, swift conveyances, canals, and ultimately railways arise, with their adjuncts of carriers and couriers, and post-establishments, and telegraphs of even greater ingenuity and efficiency.

Exchange, which was at first confined within the limits of one country, soon extends to other countries, with an immense advantage to all, for all are thus made partakers in the productions of each, which are more and more diverse according to the diversity of climate. Foreign commerce, with all that it involves of ships, docks, and warehouses, is the most powerful stimulus to home industry. But exchange, whether at home or abroad, is in all cases simply each man's giving something that he wants less, for something else that he wants more.

As geographical knowledge and means of transit are increased, numbers pass from one country to another; from countries densely peopled to those less so-from countries where land is all appropriated, to those where it is still unclaimed-from countries where capital and labour are comparatively unproductive, to those where both are more amply rewarded; new fields being thus perpetually opened up for human industry, and increased enjoyment provided by fresh and ever augmenting interchange, both for those who go and for those who stay.

But long ere this stage of progress has been reached, the precious metals themselves have been found incompetent to discharge the full duty of exchange; and paper money, or duly vouched promises to pay money, is introduced with a still more complicated machinery of bank-notes and bills of exchange, for the management of which class of transactions a still further division of labour is introduced by means of bankers, bill-brokers, and the other agents by whom, what we comprehensively call credit is carried on.

But life and property are subject to contingencies which involve serious loss, and which it is impossible always to prevent. It is discovered that the evil results to individuals, which would be ruinous to one, may, by combination, be distributed over many. Hence insurances against fire, against death, against disaster at sea, against hail storms, and diseases among cattle, against railway accidents, and even against fraud on the part of clerks and other assistants, all of which are based on calculation of averages, this again

being based on the conviction that a certain regularity prevails among events even the most anomalous and irregular. And thus, step by step, by a strictly natural course, does the work of industrial progress go on, till we witness its gigantic results in our own time, and in our own land. DR. HODGSON.

THE BROKEN HEART.

EVERY one must recollect the tragical story of young Emmet the Irish patriot; it was too toúching! to be soon forgotten. During the troubles in Ireland, he was tried, condemned, and éxecuted, on a charge of treason. His fátel made a deep impression on public sympathy. He was so yoùng-so intelligent so génerous-so bràve-so èverything that we are apt to líke in a young man. His conduct under tríal, too, was so lofty and intrèpid. The noble indignation with which he repelled the charge of treason against his country, the eloquent vindication of his name, and his pathetic appeal to posterity, in the hopeless hour of condemnation-àll thése entered deeply into every generous bòsom, and even his enemies lamented the stern policy' that dictated his execùtion.

But there was one heart! whose ánguish it would be impossible to describe. In happier dàys and fairer fórtunes, he had won the affections of a beautiful and interesting girl, the daughter of a late celebrated Irish bàrrister. She loved him with the disinterested férvour of a woman's first and early love. When every worldly maxim arrayed itself against him, when he was blasted in fortune, and when disgrace and danger darkened around his name, she loved him the more árdently for his very sufferings. If, then, his fate could. awaken the sympathy even of his foes, what must have been the agony of hér! whose whole soul was occupied by his image! Let those tell who have had the portals of the tomb suddenly closed between them and the béing' they most loved on eàrth-who have sat at its threshold, as one