them the annual cycle is rigidly observed, which, in every instance, is beautifully, and with most obvious intention, suited to the weather and other circumstances in the different localities, and the respective seasons of the year.

In autumn, while the days are still glowing with brightness and warmth, and the thermometer has scarcely begun to indicate any decrease of temperature,-when the only perceptible change is some encroachment of the night on the day,—and when the weather, in all its properties, is not less genial than during the most favourable period of summer, a very remarkable alteration takes place in the physiological condition of plants, proving that this condition is regulated by a law which is independent of external circumstances, and yet bears a striking reference to them. The alteration to which I allude is a diminution, and at length a total suspension, of the flow of sap from the roots on which the vegetative process depends; and the thing to be remarked is, that this relation is prospective. The period has not yet arrived for which this preparation is made, but is only approaching. One important and early consequence of this diminished action, is the ripening of the fruits and seed. It has been found, indeed, that, within certain bounds, whatever diminishes the vigour of vegetation, hastens the maturity of the fruit. Thus gardeners know that, by stripping trees of their leaves, the period of ripening the fruit may be hastened; and this effect is not produced so much by exposing the fruit to the influence of the sun, as by interrupting the flow of the sap. Hence it appears that the maturity of the fruit is a proof that the vital power has become less vigorcus, and is hastening to a state either of extinction, if the plant be annual, or of comparative repose if it survive the winter. This is particularly obvious in the ripening of grain. The plant loses its verdant colour, the. straw becomes less succulent, the leaf shrivels, the seed becomes hard, every thing, in short, indicates that the

VOL. IV.

B

sap has ceased to flow, that its vegetative power is exhausted, and, having fulfilled the object of its creation, that it has run its destined course.

Nothing, indeed, can be more indicative of a Designing Cause than the fact, that all plants, as soon as their annual growth and reproduction have been accomplished, decay either in whole or in part; and that, in the great majority of instances, these purposes are only consummated a short time previous to the period when the severity of coming winter would, had their cycle been protracted, have prematurely checked their progress, and rendered the labours of the year abortive.

Besides the ripening of seeds and fruits, another preparation for approaching winter, which takes place at a later period of the season, is the fall of the leaf. This, also, is a wise provision of the Creator to fit the vegetable world for encountering the storms which, in the inclement season, they are destined to endure. Some plants and trees, indeed, do not cast their leaves at this season; but even these exceptions afford, as I have elsewhere shown, a new proof of Designing Intelligence, compensating conditions having been assigned to them. To account, on physiological principles, for this fall of the leaf, various theories have been formed. Some have ascribed it to defective transpiration, and consequent accumulation of juices in the vessels; others to an inequality of growth between the stem and petiole of the leaf during the progress of vegetation; others to the drying and hardening of the cellular tissue, supposed to take place at the insertion of the petiole into the stem; others to a simple sloughing of worn out parts; and others to the growth of the new bud, and a consequent diversion of the sap. But whatever may be the immediate causes, the effect itself is, assuredly, dependant on the constitution originally imparted to the plant, and is not the less a proof of Creative Wisdom. This is, in fact, only a single instance of a universal law by which the parts of vegetables decay in every step of their pro

gress, after having fulfilled their allotted functions. Thus, the tunics of the seed perish in the earth, after having nourished and protected the germ in its earliest development. A similar fate awaits the cotyledons, which push themselves into the air when they are no longer necessary for supplying the place of leaves. The petals of flowers, also, with their stamens and pistils, wither and fall when the foundation of the seed has been effected; and when at last the fruit has arrived at maturity, it likewise separates from the parent plant or tree, and drops to the ground.

I have already remarked, that the duration of the stem and branches is very different in different plants. The longevity of some trees is very remarkable. The following notice is taken from the article " Vegetable Physiology," in the supplement to the Encyclopædia Britannica. "The Gentleman's Magazine for 1762, contains an account of the age of a chesnut-tree, then growing at Tamworth, in Staffordshire. This tree, it is said, was, at that period, probably the oldest, if not the largest, in England, being fifty-two feet in circumference. Its period of rising from the nut may be fixed at the year 800, in the reign of King Egbert. From that date to the reign of King Stephen is 335 years, at which time it was fixed on as a boundary or landmark, and called, by way of distinction, the Great Chesnut Tree of Tamworth.' From the first year of Stephen (anno 1135) to 1762, is 627 years, so that its entire age at that period was 962 years. It bore nuts in 1759, from which young trees were raised."

It is probable that some kinds of trees which are natives of more genial climates are even longer lived than the great tree of Tamworth. It is interesting to know, that there are olive trees of a most venerable age now growing in the garden of Gethsemane, near the bottom of the Mount of Olives, which are supposed to have sprung from the roots of those that existed there during our Saviour's life. The conjecture is founded on the

known longevity of the olive. The historical fact, that, during the siege of Jerusalem, Titus cut down all the trees in the neighbourhood of that devoted city, seems to preclude the possibility of their being the very individual trees whose boughs shaded the Divine Sufferer in his agony; but yet there is something which wonderfully excites the imagination, in the fact, that after the lapse of more than seventeen centuries, scions of those venerable olives should still be in existence to mark the sacred spot.

FIRST WEEK-FRIDAY.

PROGRESS OF VEGETATION IN THE CORN PLANTS.

HAVING now arrived at the season when the different kinds of corn have arrived at maturity, it may be interesting to look back on the various steps by which the vegetative process has been completed. In this retrospect, we shall constantly be reminded of the Creative Intelligence and superintending care of the God of the Seasons.

I have, in the "Spring" Volume, taken some notice of the nature and productive qualities of cultivated grain, as well as of the history of the various species, as articles of agriculture. What I intend to do at present, is to trace the seed in the progress of its development, from the period in which it is thrown into the prepared soil, till that in which it becomes ripe for the sickle. Of all the kinds of corn grown in Europe, that of wheat is not only the most valuable, but the longest attached to the soil before it arrives at full perfection. I shall confine myself, therefore, to this species of the cereal plants,— premising, that the physiological history of wheat is, with some slight exceptions, nearly identical with that of its kindred tribes.

Wheat is generally sown in the last weeks of autumn, so as to pass through the first important steps of the vegetative process before the severity of winter sets in. In its earliest growth, there is little peculiar. Like other seeds, whose development has been described in a previous volume, it consists of a bud containing the embryo of the future root and plumale, wrapt up in integuments, and lying between, but at one end of the cotyledons, which serve as its first nourishment. When the seed has been in the ground for about two days, it begins to swell, and the juices contained in the cotyledons, being communicated to the bud, produce in it the first vegetative motions, and cause it to shoot out its root and plumale. The root is at first wrapt up in a kind of purse, through which it forces its way. Two other roots spring forth in a lateral direction, within a few days, and burst through the texture which covered them, now softened by the moisture of the earth in which they are buried. Each of the roots is shagged with a number of fibres, which closely twine about the particles of earth presented to them in their progress, and extract from them whatever is capable of nourishing the young plant, in conjunction with the fluids which it still derives from the inward substance of the seed.

Meanwhile the plumale shoots upwards in as direct a line as circumstances will admit, protected by a little tegument, which withers away when its services are no longer required. In favourable circumstances, the corn will begin, about the sixth or seventh day, to push its verdant point through the surface of the earth. This feeble stem is nothing more than a bundle of leaves folded over each other, and around the delicate embryo which is to form the future spike. The first leaf of this packet opens a little toward the point, but its lower part is always rolled up in the hard covering from whence it springs. In a few days after the stem emerges to the light, the seed, which has been gradually giving out its

* "Spring,"-Paper on the Development of Seeds and Plants.