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which at certain seasons become dry; and the beds of these canals, which quickly become burnt as hard as bricks by the action of the sun, are then used as carriage-roads. When the water is again admitted the plant resumes its growth with redoubled vigour.

To suit all the varied conditions to which I have thus briefly alluded, and under which plants are found to exist; they have been formed by their Almighty Creator of different structures and constitutions, to fit them for the stations they severally hold in creation; and so striking are the results, that every different region of the globe is characterized by peculiar forms of vegetation. A practised botanical eye can with certainty, in almost all cases, predict the capabilities of any hitherto unknown country, by an inspection of the plants which it produces. It were much to be wished, that those upon whom the welfare of thousands of their starving emigrant countrymen depends, possessed a little more of this most useful knowledge. But in order to give us a clearer idea of the “strong connexions, nice dependencies," existing between climate and vegetation, let us survey plants in a state of nature. We shall find some restricted to certain situations, while others have a wide range, or greater powers of adaptation. It is not perhaps going too far to assert, that no two plants are alike in this particular, or in other words, that the constitution of every individual plant is different. Of the former, Trichomanes speciosum is an example, it not being able to exist, even for a short time, in a dry atmosphere: of the latter, familiar examples are presented to us in the London Pride and the Auricula; these of course grow in greater or less luxuriance, as the conditions are more or less favorable. The Cerasus Virgi

I have ga

niana affords an interesting illustration of the effects of climate upon vegetation : in the southern states of America it is a noble tree, attaining one hundred feet in height; in the sandy plains of the Saskatchawan it does not exceed twenty feet; and at its northern limit, the Great Slave Lake, in lat. 62°, it is reduced to a shrub of five feet. But we need not travel to America to seek instances of this sort: we have them every where about us. thered, on the chalky borders of a wood in Kent, perfect specimens in full flower of Erythræa Centaurium, not more than half an inch in height, consisting of one or two pairs of most minute leaves, with one solitary flower: these were growing on the bare chalk. By tracing the plant towards and in the wood, I found it gradually increasing in size, until its full development was attained in the open parts of the wood, where it became a glorious plant, four or five feet in elevation, and covered with hundreds of flowers. Let us pause here a moment, and reflect deeply on the wonders around us. We shall find a continued succession of beauties throughout the year, beginning with the Primrose, the Violet, and the Anemone; these giving place to the Orchises ; and these again to the Mulleins, Campanulas, and various other plants, all in their turn delighting the eye and gladdening the heart: nor is the winter season devoid of interest; the surface of the ground, and every decaying leaf and twig, is inhabited by a world of microscopic beauties. All these have maintained their ground, without interfering with each other, year after year and generation after generation. The same page in the great book of nature, which filled the mind of Ray with the Wisdom of God in Creation, lies open to our view. May we read it aright! Let us ask ourselves,

whether man, with all his boasted wisdom, can realize such a scene as this? He cannot,—and the cause lies in his ignorance of the natural conditions of plants. To sum up in the words of a great philosopher of the present day.“If the laws of nature, on the one hand, are invincible opponents, on the other they are irresistible auxiliaries; and it will not be amiss if we regard them in each of these characters, and consider the great importance of them to mankind.

“ Istly. In showing us how to avoid attempting impossibilities.

“ 2dly. In securing us from important mistakes in attempting what is in itself possible, by means either inadequate, or actually opposed to the ends in view.

“ 3dly. In enabling us to accomplish our ends in the easiest, shortest, most economical and most effectual manner.

“4thly. In inducing us to attempt, and enabling us to accomplish objects, which, but for such knowledge, we should never have thought of undertaking."-Herschel.

CHAPTER II.

ON THE CAUSES WHICH INTERFERE WITH THE NATURAL

CONDITIONS OF PLANTS IN LARGE TOWNS.

“ As well might corn, as verse, in cities grow;

In vain the thankless glebe we plough and sow :
Against th' unnatural soil in vain we strive ;
"T is not a ground in which these plants will thrive."

Cowley.

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