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LESSONS IN BOTANY.-III.
gress, the winter to which they are exposed being so short, that
their course of growth is scarcely interfered with by any im. SECTION IV.-STRUCTURE OF THE STEM OF VEGETABLES. I pediment. Under these circumstances, there is scarcely any This is a very important point, and helps to furnish us with a winter pause sufficient to create a line of demarcation between means of dividing plants, at least flowering plants, into two ring and ring; the progress of deposition goes on continuously, primary groups or divisions. Let us consider that which takes However, the manner of deposition is not the less external be place during the growth of an oak from the acorn. The acorn, cause we cannot see the rings. on being planted in the ground, sends down its root, and sends Very different from this method of increase is that by which up its stem. At first this stem is a tiny thing of very incon- another grand division of plants augments in size. For an ex. siderable diameter; year by year, however, it grows, until a ample we must no longer have recourse to a section of a plant gigantic tree results. If we now cut this tree across and examine of our temperate zone, but must appeal to the larger tropical the structure of its section, we shall recognise the following ap- productions of this kind. If we cut a piece of bamboo, or cane pearances. In the first place, commencing our examination from (with which most of us are familiar), horizontally, we shall find without, we shall find the bark, or cortex (Latin, cortex, bark), a very different kind of structure to that which we recognised separable into two distinct layers, the outer of which is termed in the oak. There will be no longer seen any real bark, nor any the cuticle (Latin, cutis, skin), or epidermis, (Greek étudepuis, pith, and the concentric rays will be also absent, but the tissue pronounced ep-i-der-mis, the outer skin), and the inner one the of which the stem is made up may be compared to long strings liber, so called becanse
of woody fibre tightly the ancients occasionally
packed together. These employed this portion of
concentric rings, in point the bark as a substitute
of fact, could not have for paper in the making
existed ; inasmuch as a of booksliber being the
cane does not grow by Latin for book. Passing
deposition of woody matFards, we observe the
ter externally, but interFoody fibre and its cen.
nally, or, more properly tral pith. The woody
speaking, upwards. A fibre itself is evidently of
young cane is just as big two kinds, or at least is
round as an old cane, 80 put together that wood
the only difference beof two degrees of hard.
tween them consisting in ness results. The exter
the matters of hardnoss nal portion of wood is the
and of length. Hence, softer and lighter in col.
bamboos, and all vegeour, and termed by bota
tables which grow by nists alburnum, from the
this kind of increment, Latin word albus, white;
are termed endogenous, the internal is the harder,
from two Greek words and termed by botanists
évboy (en'-don), within, duramen, from the Latin
and yevvda (gen-ná-o), I durus, hard, although car.
generate. The largest penters denominate it
specimen of endogenous heart-icood. Lastly, in
growth is furnished by the centre comes the pith
palm trees—those magni. or medulla, from the
ficent denizens of tropical Latin, medulla, the mar
forests to which we are row, which traces its ori.
so much indebted for ginto another Latin word,
dates, cocoa-nuts, palmmedirls, the middle, the
oil, vegetable wax, and marrow being in the mid
numerous other useful dle of the bone. Regard.
products. Fig. 11 is a reing this section a little
presentation of the secmore attentively, we shall
tion of a palm tree, in observe passing from the 10. HORIZONTAL SECTION OF AN EXOGEN. 11. HORIZONTAL SECTION OF AN ENDOGEN, which the peculiarities of Dith to the bark and 12. DOTTED VESSELS OF THE CLEMATIS. 13. DOTTED VESSELS OF THE MELON 14. endogenons structure are establishing a connexion
SPIRAL VESSELS OF THE MELONS. 15. LACTIFEROUS VESSELS OF THE CELANDINE, very well developed
16. OVOID CELI, 17. STELLIFORM CELLS. 18. ANGULAR CELLS. between the two, a series
All the endogenous proof white rays, termed by
ductions of temperate the botanist medullary rays, and by the carpenter silv. climes are small, though very important. In proof of the latter grain. We shall also observe that the section displays a series assertion it may suffice to mention the grasses; not only those of ring-like forms concentric one within the other. These are dwarf species which carpet our lawns and our fields with verdure, 2 very important characteristic. They not only prove that but wheat, barley, oats, rice, maize, all of which are grasses, the trunk in question was generated by continued depositions botanically considered, notwithstanding their dimensions. Inof woody matter around a central line, or, in other words, by an deed, size has little to do with the definition of a grass ; for if we outside deposition, but they enable us in many cases actually to proceed to tropical climes, we shall there find grasses of still more read off the age of any particular tree—the thickness cor- gigantic dimensions. Thus the sugar cane, which grows to the responding with one ring being indicative of one year's growth. elevation of fifteen or sixteen feet, is a grass, as in liko manner Inasmuch as the formation of an oak tree is thus demonstrated is the still taller cane, out of the stem of which, when split, we to be the consequence of a deposition of successive layers of make chairbottoms, baskets, window-blinds, etc., and which, woody fibres externally or without-it is said to be like all when simply cut into convenient lengths, is also useful for other others subjected to the same kind of growth, an ecogenous plant, purposes; one of which will, perhaps, occur to some of our from two Greek words, tw (ex'-o), without, and gevrów (gen- ' younger readers. add, g hard, as in guen), I generate.
The reader will not fail to remember that we, a few pages Fig. 10 represents the internal structure of an exogenous back, divided vegetables into phænogamous and cryptogamic stem.
(we are sure we need not repeat the meaning of these terms). It is true that the peculiar disposition of rings thus spoken We may now carry our natural classification still further, and of cannot always be recognised. For example, as a rule, trees say that phænogamous plants admit of division into exogenous which grow in hot climates are checked so little in their pro- and endogenous ones. This division is quite natural, even if we
B u yone of the stem; but the ' an example the reader may refer to an orange, especially an
Anot mengirable by other orange somewhat late in the season. If the fruit be out, or, still * * *y* What we come to consider better, paded ssunder, the cells will be readily apparent. .
Still V und Aperta
| more realizy do they admit of being observed in that large
species of the orange tribe to which the name shaddock, or I m AVE AND THEIR CIES. fcroviden fruit is ordinarily given.
* We must now inform the reader that not only do the cells of ating the lature of a thing; one this sectiar tisse zutenit of being altered in form, but occa
***unt.A. Of hete the latter is iobally they give rise to parts in the vegetable organisation - a former in the more precise which poi sot be scapected to consist of cells. The cuticle of
sullummanca y tating that in which we have spoken is nothing more than a layer of cells
s ata terinition 1 - 2 thin firmly wharent; and the medallary rays, or silver grain, of • Imu. ontaining between ita two exogenous tems. the appearance of which has been already
** _ne, servos, and reins, and per- dieser bei is acting Dore nor less than closely compressed _-: tuation ind respiration." Such is ceilniar site.
.: 88. Probably the learner may Wa commencei be describing a leaf, but observations have - t t tt a little contemplation, been con tracted to matters collateral to the subject that - Free Dject of enabling um to the ieserptea appears somewhat rambling. Nevertheless, it
onge we go through its clauses one cannot be cipech In Botany, above all other sciences, there - 2 yttenert sipawn of putere, oceur many croce names. They must be learnt, and the best
tent xpression. The epidermis vay anh em is to describe them as they occur. - **ated. the outside hark-at least.' A 'esf. then, we repest, is an extension of two flat sarfaces of
9.- 20. Literally, the Greek wori euticie enciosing nerves and veins, vascular and cellular tissue. ... m e d bove, and is also appliet il nese teens have been pretty well explained. We may add. .
19 animai, skin which readily peels flowever, tant en eelzlar tissue exists confusedly thrown
c ount blister, and whion. When Dgether. 3 it does in the substance of a leaf, or as it appears ....M
a tules chose troublesome peste on D he range, then sich cellular tissne is denominated paren, - " regards the epidermis
u m Ifrom the Greek word Taper xua (pronounced par-en.. . .
Te en in the birch tree. trom win 7 6 -) *212y i pored out."
Tonitrit, thon, consists of two Before we pude tinish with our remarks relative to the sub.... we suv i the other blow, BASEL) Tunces which enter into leares, it is necessary to observe that
2 ng wiuca terms we wave se pren diotras matter of leaves is termed by botanists and
te wori 143Chur means " CUB by humnists***84) , from the two Greek words xawpós (prowas and start ved from 20 Lunin mundesi rusi. yelowish green, and pullos (pronounced within the lisede mandl, VILA "Il derived from the dini. sent. Thus chlorophyl is subject to become sienna. .. ab
sisting of in atmn, $$ we 1 know, but the cause of this alteration ...
I a muselttie pipes or tubus aut vat been explained. . S tel Ostiku arteries and veins
eta e serve the purpose conmodel
tab a nt to mother. In plants,
IV. THE COMMA.
Le lieben wing
r esso a trova Cum Tut is a round dot with a small Ben 10 a v tead, WARAS is 2
"Le rulat to LED from right to left. e nel nostro canale blow truccok kot 3. Who you come to comma in reading, you must, in
Am Waddene k a n ik fenn, naky short pause or stop, so long as would enable
Treast wort before a comma is most frequently read d iode, dubbel e am 21** *£ with healing antiaction of the voice.
Han Won beide sist e tiden 3. ? Un vien you come to a comma, you must keep o r 'n wonder
h at Vr von sexenetewi 38 if some one had stopped you before you WA
SI M AK ****** oldin un an la you intended to read. i ráda a prevede body hipopo UNE V tom in the fouiuwing examples keep your breath suspended
Pony w 1846 dakika ya WC, LU , WABARD me the comma ; but let the short pause or stop at in s
ob **** W lavd you be a tutai cessation of the voice. * benean tiga landslide wall on me
Examples. . ita tak ta a ta
iputstry, and proper improvement of time, are material no s' in all side
wissabon, dy art, by the united strength of a civil community, la * Den epabled to subdue the whole race of lions, bears, and
there is no pause in the book. Spaces are left in the following Did you rend as correctly, speak as properly, or behave as well as i sentences where the pause is proper to be made. James ?
Examples. Art thon the Thracian robber, of whose exploits I have heard so
The Europeans were hardly less amazed at the scene now set much?
before them. Who shall separate us from the love of Christ ? shall tribulation,
Their black hair long and curled floated upon their or distress, or persecution, or famine, or peril, or sword ?
shoulders or was bound in tresses around their head. How are the dead raised up, and with what body do they come ?
Persons of reflection and sensibility contemplate with interest For what is our hope, our joy, or crown of rejoicing ?
the scenes of nature. Have you not misemployed your time, wasted your talents, and
The succession and contrasts of the seasons give scope to care passed your life in idleness and vice ?
and foresight diligence and industry which are essential to the Have you been taught anything of the nature, structure, and laws
dignity and enjoyment of human beings. of the body which you inhabit ? Were you ever made to understand the operation of diet, air, | It is grateful to perceive
The eye is sweetly rested on every object to which it turns.
how widely yet chastely Nature hath exercise, and modes of dress, upon the human frame ?
mixed her colours and painted her robe. 28. Sometimes the word preceding a comma is to be read Winter compensates for the want of attractions abroad by fire. like that preceding a period, with the falling inflection of the side delights and homefelt joys. In all this interchange and voice.
variety we find reason to acknowledge the wise and benevolent Examples.
caro of the God of seasons. It is said by unbelievers that religion is dull, unsociable, uncharitable, 32. The pupil may read the following sentences; but before enthusiastic, a damper of human joy, a morose intruder upon human reading them, he should point out after what word the pause pleasure.
should be made. The pause is not printed in the sentences, but Nothing is more erroneous, unjust, or untrue, than the statement it must be made when reading them. And here it may be in the preceding sentence.
observed, that the comma is more frequently used to point out Perhaps you have mistaken sobriety for dulness, equanimity for
sobriety for dwness, equanimity for the grammatical divisions of a sentence, than to indicate a rest moroseness, disinclination to bad company for aversion to society,
or cessation of the voice. Good reading depends much upon abhorrence of vice for uncharitableness, and piety for enthusiasm. Henry was careless, thoughtless, heedless, and inattentive.
skill and judgment in making those pauses which the meaning This is partial, unjust, uncharitable, and iniquitous.
of the sentence dictates, but which are not noted in the book; The history of religion is ransacked by its enemies, for instances of and the sooner the pupil is taught to make them, with proper persecution, of ansterities, and of enthusiastic irregularities.
discrimination, the surer and more rapid will be his progress in Religion is often supposed to be something which must be prac- the art of reading. tised apart from everything else, a distinct profession, a peculiar
The golden head that was wont to rise at that part of the table was 29. Sometimes the word preceding a comma is to be read
now wanting like that preceding an exclamation.
For even though absent from school I shall prepare the lesson.
For even though dead I will control the trophies of the capitol. Escamples.
It is now two hundred years since attempts have been made to How can you destroy those beautiful things which your father civilise the North American savage, procured for you! that beautiful top, those polished marbles, that Doing well has something more in it than the fulfilling of a duty. Excellent ball, and that beautifully painted kite, oh how can you de.
You will expect me to say something of the lonely records of the stroy them, and expect that he will buy you new ones!
former races that inhabited this country. How canst thou renounce the boundless store of charms that
There is no virtue without a characteristic beauty to make it partiNature to her votary yields! the warbling woodland, the resounding
cularly loved by the good, and to make the bad ashamed of their shore, the pomp of groves, the garniture of fields, all that the genial
neglect of it. ray of morning gilds, and all that echoes to the song of even, all
A sacrifice was never yet offered to a principle, that was not made that the mountain's sheltering bosom shields, and all the dread
up to us by self-approval, and the consideration of what our degradamagnificence of heaven, how canst thou renounce them and hope to tion would have been had we done otherwise.' be forgiven!
The succession and contrast of the seasons give scope to that care O Winter! ruler of the inverted year! thy scattered hair with sleet
and foresight, vigilance and industry, which are essential to the dignity like ashes filled, thy breath congealed upon thy lips, thy cheeks fringed
and enjoyment of human beings, whose happiness is connected with with a beard made white with other snows than those of age, thy the exertion of their faculties. forehead wrapped in clouds, a leafless branch thy sceptre, and thy
A lion of the largest size measures from eight to nine feet from throne a sliding car, indebted to no wheels, but urged by storms along the muzzle to the origin of the tail, which last is of itself about four its slippery way, I love thee, all unlovely as thou seemest, and dreaded feet long. The height of the larger specimens is four or five feet. as thou art !
A benison upon thee, gentle huntsman! Whose towers are these Lovely art thou, O Peace! and lovely are thy children, and lovely
that overlook the wood ? are the prints of thy footsteps in the green valleys.
The incidents of the last few days have been such as will probably 30. Sometimes the word preceding a comma and other marks, never again be witnessed by the people of America, and such as were is to be read without any pause or inflection of the voice.
never before witnessed by any nation under heaven.
To the memory of André his country has erected the most m Examples
cent raonument, and bestowed on his family the highest honours You see, my son, this wide and large firmament over our heads, and most liberal rewards. To the memory of Hale not a stone has where the sun and moon, and all the stars appear in their turns. been erected, and the traveller asks in vain for the place of his long Therefore, my child, fear and worship, and love God.
sleep. He that can read as well as you can, James, need not be ashamed to read alond. I consider it my duty, at this time, to tell you that you have done
MECHANICS.-III. something of which you ought to be ashamed. The Spaniards, while thus employed, were surrounded by many of
FORCES APPLIED TO A SINGLE POINT---PARALLELOGRAM the natives, who gazed, in silent admiration, upon actions which they
OF FORCES, ETC. conld not comprehend, and of which they did not foresee the conse In this lesson we have to consider how the resultant of two, and quences. The dress of the Spaniards, the whiteness of their skins, thence of any number of forces, applied to a single point may be their beards, their arms, appeared strange and surprising
found. You will keep in mind that by a "single point," I mean Yet, fair as thou art, thou shunnest to glide, beautiful stream! by the village side, but windest away from the haunts of men, to silent
a point" in a body;" and that will savo mo always adding the valley and shaded glen.
latter words when I use the former. Of course, forces applied But it is not for man, either solely or principally, that night is
| to “a material point” are included in the description, and made.
theso you will find, in due time, to be of very great importance. We imagine, that, in a world of our own creation, there would As the joint effect of two or more forces so applied is termed always be a blessing in the air, and flowers and fruits on the earth. | their “resultant," so we name the separate forces of which it is
Share with you! said his father-so the industrious must lose his the effect its components. There are thus two operations, the hbour to feed the idle.
Composition of Forces, and the Resolution of Forces, with which 31, Sometimes the panse of a comma must be made where we may be concerned in Mechanics; by the former of which we
at their ant sie simmetristely sy, a in e vet in B, then be 22
fe N orge, si me acomi is the mycirel Paugeran Lirus furined is e . Sot so . Tot seei act be the whole of that wimww wind for 6202, of v Pand i ri22. 3 5 :I hea S., S he end of you
Now, I shall not here in 3 para sa
3, it is sia
I triar gle so formed by joining the end of this line with the point
lines, which, as you will see, when many forces have to be com- all its angles equal; also the angles between the sides of the pounded, would cause much confusion in your figures. . triangle, or of the polygon of forces, are the angles between the
Let us apply this principle now to compound any number of forces themselves, since they are parallel to these forces. This forces acting on a point. Let there be five, and that will illus- is evident from the properties, 1 and 2, of the parallelogram trate the rule as well as a thousand could. Suppose forces, O A, referred to above; therefore, in the case we are considering, the
OB, O C, OD, O E, ap- three equal forces must act at equal angles, as I showed other-
let us suppose it drawn. points of support of the strings which meet at o. Now, whatFig. 6.
Now, if I compound this ever be the strains on the cords, O P, 0 Q, they make equilibrium resultant with o c, I have with w, the weight. Therefore, if we suppose a length, o A, of the resultant of three of O p to represent the strain
the forces. But that, by on O P, and from a draw a the same rule, is got by drawing from R a line R r, equal line, A E, parallel to o Q,and parallel to o C. The line o R is this resultant of three. equal to the strain, OB, Again we shall not draw it. The resultant of this and o D, ono q, then, since the three for the same reason, would be o B., got by drawing R, R, forces are in equilibrium, parallel and equal to o D, and, lastly, the resultant of this the line, R o, closing up the and o E would be o Rze the line, R, Rg, being equal and triangle must be equal to, parallel to o E. We have thus exhausted all the forces, and be in the direction as, and evidently o R, is the resultant of the whole five. There the third force, or weight, w. was here no confusing ourselves with parallelograms; all we This, then, tells us what to had to do was to draw line after line, one attached to the do. Measure on o R upward other, carefully observing to keep their magnitudes and direc- as many inches as there are tions aright. A kind of unfinished polygon was thus formed, and pounds in w; and from R the line o Ry, which closes up the polygon, joining the last point then draw R A parallel to
Fig 7. Ry, with the point of application, is the resultant in magnitudo the cord o to meet the cord o A. The number of inches in and in direction. Thus you have made another step in advance, O A will represent in pounds the strain on O P, and those on and arrived at the Polygon of Forces. You have learned how, R A the strain on o Q. All, therefore, that we desire to know is by the mere careful drawing of lines, to determine the resultant determined. of any number of forces. All you require is paper and pencil, Third Example.-A horse pulls a roller up a smooth inclined a rule, compasses, a scale, and a pair of parallel rulers.
plane or slope; what is the force he must exert when he just Now, there is one point about this polygon I wish you keeps the roller at rest ? And by how much does the roller carefully to note. You will observe that the arrows on its press on the plane ? sides, representing the directions of the forces you have com- Let the horse pull in any direction, o A. Then there will be pounded, all point from left to right, as you go round the figure, three forces acting on the roller, namely, its own weight right turning it with you so as to bring each side in succession to the downwards, the horse's pull, and the resistance of the plane or top. The resultant, however, points in the opposite direction, slope, perpendicular to itself. There must be this third force, from right to left, when that side is uppermost. This is as it for the other two, should be ; the direction of the resultant, as you go round the not being opposite figure, must be opposite to those of the components. The use of to each other, can. this you will see in the next lesson.
not make equili. Now, let us suppose that, in determining the resultant after brium. The roller this method, as we come to the end of the operation, the end, is somehow supPs, of the last line, R, Ry, chanced to coincide with, or fall upon ported by the plane; the point of application, o. The polygon would close of itself and that it cannot without any joining line; what is the meaning of this? It be unless by its remeans that there is no resultant; the line, o Rg, is nothing, and sistance ; and a therefore the resultant is nothing, and the forces produce equili- plane cannot resist brium. What a valuable result we have arrived at! A method except perpendicu. by which we can, by rule and compass, tell at once whether any larly to itself. This number of forces make equilibrium at a point or not. All we third force, you
Fig. 8. have to do is to describe the polygon of forces, and if it closes thus see, must be up of itself, there is equilibrium ; if it does not, there cannot be taken perpendicular to the plane. It is represented in the eqnilibrium, and the resultant is in magnitude the side which is figure by 0 B. Now apply the polygon of forces. Let oc nedessary to close the figure.
represent the weight of the roller, and from c suppose a Deferring the further expansion of this subject to the next line, CR, drawn equal and parallel to o A, the horse's pull. lesson, I shall now turn back and apply these principles to a few Then, since there is equilibrium, the polygon of forces should elementary examples.
close up and become a triangle—that is, the line joining R First Example.-Three equal forces act at a point in different with o should be the pressure, and therefore should be perdirections—what condition should they fulfil in order to be in pendicular to the plane. What then are we to do? Take equilibrium ? Get your ruler and compass, and commence o C, equal in inches to the number of pounds in the roller, constructing the figure by which their resultant may be found. draw then from c a line c R parallel to the horse's pull, to From the end of one of the forces you are to draw a line equal meet the line drawn from the centre o of the roller perpenand parallel to the second equal force, and from the end of that dicularly to the plane ; C so determined will in inches tell another line, equal and parallel to the third. You will thus the pounds in the horse's pull, and o R the amount by which have three lines strung together, all equal to each other. But the roller presses the plane. You can easily see from this that if the forces are in equilibrium, the end of the last line must as the slope increases the pull will increase and the pressure fall on the point of application, that is to say, the polygon of diminish. This is what naturally we should expect. The plano forces must close up, and form a triangle. Your construction I have supposed to be smooth; for, where there is friction will then give you a triangle of three equal sides, commonly against the roller caused by roughness in itself or in the plane, or called an equilateral triangle. But such a triangle must have in both, the question is much altered, as in due time you will see.