LECTURE V.

THE STUDY OF NATURE, whether of vegetable, animal, or mineral, is not only a pleasing occupation, profitable one, inasmuch as it is eminently inIt elevates the heart while it expands

but a

structive.

and enlightens the mind, and leads it properly to estimate the infinite and almighty power of a Superior Superior Being; and to think humbly of himself whilst looking up to the great Creator of the

universe.

in the plants and herbs which surround us on every It may truthfully be said that there are sermons side; for who can examine the economy displayed in the formation of the least of these things without being astonished at the completeness of its form for the purpose for which it was designed.

All

men of eminent acquirements, from the earliest

periods, have more or less studied nature; and who can doubt that our Saviour Himself desired to direct His disciples to the importance of the study of nature, he peruses that beautiful passage in the twelth chapter of St. Luke and other parts of the Scriptures.

Consider the lilies of the field, how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these."-How very true! for, what is the

fabric of even the most gorgeous robes of royalty, when compared with the delicate fibres or veins of this very beautiful flower!

To enter very minutely into all the particulars of the form and duration of trees and plants would require a series of lectures; my object is more to bring before you a brief notice of some of the leading features in their formation, as instructive information to those who have not before had their attention drawn to the study of the nature and properties of plants, and to create in them a desire to think and study for themselves.

The existence of all vegetables may be regarded as mechanical, or as similar to that of an animal when asleep, during which time his functions proceed without consciousness.

In a short period after a seed is thrown into the earth, the two ends open; from one of them issues a green plant, and from the other a number of fibrous threads; and, whatever may be the position of the seed, the green sprout struggles through the soil upwards into the air; and the fibrous shoots strike downwards into the ground, and it is the office of the fibrous threads or roots there to imbibe the moisture, and to transmit or pump it up as nourishment to the plant.

Nothing in nature is more wonderful than the means for the preservation of seeds, and the contrivances by which they are distributed. Some are provided with downy wings, such as the lettuce and others, and are carried about by the winds-others are carried about and deposited by birds; but all are preserved by their coverings, till excited into germination by the heat of the sun's rays in the following spring. Each has its peculiar habitation; and each adapts the nutriment derived from the same earth so differently, that by an unknown agency it produces all the degrees of flavour, odour, poison, and nutriment, which we find in the various plants.

How beautifully is this described by the poet Blackmore :

:

"Each tree, each plant, from all its branching roots,
Amid the glebe small hollow fibres shoots;

Which drink with thirsty mouths the vital juice,
And to the limbs and leaves their food diffuse;
Peculiar pores, peculiar juice receive,

To this deny, to that, admittance give."

Plants are supplied with nourishment from the roots, as animals are from the food taken into the stomach; and in order to conceive an idea of the form in which plants receive nourishment, you must represent to yourselves a very delicate cobweb network, of such extreme tenuity or thinness as to render it invisible until the interstices are filled and distended by the nutriment lodged within them.

The food of plants is not like that of animals, of a complicated nature; but consists of the simplest materials, water and the solid and gaseous matter contained within it. The whole of the vegetable kingdom consists of masses of elementary organs, with the exception of mosses and such like plants, whose vessels are of a cellular form, that is, consisting of little cells or cavities; they have no vascular system, by which is meant a system filled with vessels. The fibres of plants are composed of collections of these vessels and cells closely connected together. The root and stem of plants consist of such fibres. If you attempt to cut them transversely you meet with considerable resistance, as you must force your way across the tubes and break them; whilst, if you slit the wood longitudinally, you separate the vessels without breaking them, and have only to force your way through the elongated cellular tissue which con

nects them.

The cells by the growth of the stem are frequently drawn out of their original form, but the vascular system which is of the greatest importance is internal, and lodged in a bed of cellular integuments, so that

the pressure of the bark or surrounding parts is not sufficient to crush it.

The layers of wood which you may notice in the stem or branch of a tree cut transversely consist of different zones of fibres, each the produce of one year's growth; they are separated by a coat of elongated cellular tissue, without which you could not well distinguish them.

The cuticle, which is the external covering of the plant, consists of an expansion of the cellular tissue; and is furnished with pores for evaporation. The cuticle of a young shoot, after it has been for some time exposed to the atmosphere, becomes opaque, that is, not transparent, dries, and, distended by the lateral growth of the branch, splits and after a year or two falls off. A second membrane is then formed by the desiccation, or drying up, of the external part of the cellular integument or covering; but it differs from the former in being thicker, and of a closer texture. It is not furnished with pores, having no other function to perform than to enclose a layer of air, and preserve the internal parts from injury.

These general though rather desultory observations may, I hope, be considered as preparatory to the examination of the structure of a full grown plant, beginning with the roots, and proceeding up the stem to the leaves.

In the nutrition of plants, six periods are to be distinguished.

1st. The absorption of nourishment by the roots. 2nd. The transmission of nourishment from the roots to the different parts of the plants.

3rd. The development of the nourishment. 4th. The action of the air on plants.

5th. The conversion of nourishment into returning sap.

6th. The secretion of various juices from the sap. At the extremity of each fibre of a root, there is an expansion of the cellular integument called a