Chapter II: Part 2

For illustration of this point, the careful watching of the cuttings placed in water will be very instructive. After a few days, small, hard lumps begin to appear under the skin of the stem of the broken seedling Bean. These gradually increase in size until, finally, they rupture the skin and appear as rootlets. Roots are always thus formed under the outer tissues of the stem from which they spring, or the root from which they branch. In the Bean, the roots are in four long rows, quartering the stem. This is because they are formed in front of the woody bundles of the stem, which in the seedling Bean are four. In the Sunflower the roots divide the circumference into six parts. In some of my cuttings of Beans, the stem cracked in four long lines before the roots had really formed, showing the parenchyma in small hillocks, so to speak. In these the gradual formation of the root-cap could be watched throughout, with merely a small lens. I do not know a better way to impress the nature of the root on the pupil's mind. These forming roots might also be marked very early, and so be shown to carry onward their root-cap on the growing-point.

4. _Root-hairs_. These are outgrowths of the epidermis, or skin of the root, and increase its absorbing power. In most plants they cannot be seen without the aid of a microscope. Indian Corn and Oats, however, show them very beautifully, and the scholars have already noticed them in their seedlings. They are best seen in the seedlings grown on damp sponge. In those grown in sand, they become so firmly united to the particles of soil, that they cannot be separated, without tearing the hairs away from the plant. This will suggest the reason why plants suffer so much from careless transplanting.

The root-hairs have the power of dissolving mineral matters in the soil by the action of an acid which they give out. They then absorb these solutions for the nourishment of the plant. The acid given out was first thought to be carbonic acid, but now it is supposed by some experimenters to be acetic acid, by others to vary according to the plant and the time. The action can be shown by the following experiment, suggested by Sachs.

Cover a piece of polished marble with moist sawdust, and plant some seeds upon it. When the seedlings are somewhat grown, remove the sawdust, and the rootlets will be found to have left their autographs behind. Wherever the roots, with their root-hairs have crept, they have eaten into the marble and left it corroded. The marks will become more distinct if the marble is rubbed with a little vermilion.

In order that the processes of solution and absorption may take place, it is necessary that free oxygen should be present. All living things must have oxygen to breathe, and this gas is as needful for the germination of seeds, and the action of roots and leaves, as it is for our maintenance of life. It is hurtful for plants to be kept with too much water about their roots, because this keeps out the air. This is the reason why house-plants are injured if they are kept too wet.

A secondary office of root-hairs is to aid the roots of seedlings to enter the ground, as we have before noticed.

The root-hairs are found only on the young parts of roots. As a root grows older the root-hairs die, and it becomes of no further use for absorption. But it is needed now for another purpose, as the support of the growing plant. In trees, the old roots grow from year to year like stems, and become large and strong. The extent of the roots corresponds in a general way to that of the branches, and, as the absorbing parts are the young rootlets, the rain that drops from the leafy roof falls just where it is needed by the delicate fibrils in the earth below.[1]

[Footnote 1: Reader in Botany. VI. The Relative Positions of Leaves and Rootlets.]

5. _Comparison of a Carrot, an Onion, and a Potato_.--It is a good exercise for a class to take a potato, an onion, and a carrot or radish to compare, writing out the result of their observations.

The carrot is a fleshy root, as we have already seen. The onion consists of the fleshy bases of last year's leaves, sheathed by the dried remains of the leaves of former years, from which all nourishment has been drawn. The parallel veining of the leaves is distinctly marked. The stem is a plate at the base, to which these fleshy scales are attached. In the centre, or in the axils of the scales, the newly-forming bulbs can be seen, in onions that are sprouting. If possible, compare other bulbs, as those of Tulip, Hyacinth, or Snowdrop, and the bulb of a Crocus, in which the fleshy part consists of the thickened base of the stem, and the leaves are merely dry scales. This is called a _corm_.

The potato is a thickened stem. It shows itself to be a stem, because it bears organs. The leaves are reduced to little scales (eyelids), in the axils of which come the buds (eyes). The following delightful experiment has been recommended to me.

In a growing potato plant, direct upwards one of the low shoots and surround it with a little cylinder of stiff carpet paper, stuffed with sphagnum and loam. Cut away the other tuber-disposed shoots as they appear. The enclosed shoot develops into a tuber which stands more or less vertical, and the scales become pretty little leaves. Removing the paper, the tuber and leaves become green, and the latter enlarge a little. A better illustration of the way in which organs adapt themselves to their conditions, and of the meaning of morphology, could hardly be found.

_Gray's First Lessons_. Sect. v, 65-88. _How Plants Grow_. Chap. I, 83-90.

IV.

BUDS AND BRANCHES.

1. There is an astonishing amount to be learned from naked branches, and, if pursued in the right way, the study will be found exceedingly interesting. Professor Beal, in his pamphlet on the New Botany,[1] says:--

"Before the first lesson, each pupil is furnished or told where to procure some specimen for study. If it is winter, and flowers or growing plants cannot be had, give each a branch of a tree or shrub; this branch may be two feet long. The examination of these is made during the usual time for preparing lessons, and not while the class is before the teacher. For the first recitation each is to tell what he has discovered. The specimens are not in sight during the recitation. In learning the lesson, books are not used; for, if they are used, no books will contain a quarter of what the pupil may see for himself. If there is time, each member of the class is allowed a chance to mention anything not named by any of the rest. The teacher may suggest a few other points for study. The pupils are not told what they can see for themselves. An effort is made to keep them working after something which they have not yet discovered. If two members disagree on any point, on the next day, after further study, they are requested to bring in all the proofs they can to sustain their different conclusions. For a second lesson, the students review the first lesson, and report on a branch of a tree of another species which they have studied as before. Now they notice any point of difference or of similarity. In like manner new branches are studied and new comparisons made. For this purpose, naked branches of our species of elms, maples, ashes, oaks, basswood, beech, poplars, willows, walnut, butternut, hawthorns, cherries, and in fact any of our native or exotic trees or shrubs are suitable. A comparison of the branches of any of the evergreens is interesting and profitable. Discoveries, very unexpected, are almost sure to reward a patient study of these objects. The teacher must not think time is wasted. No real progress can be made, till the pupils begin to learn to see; and to learn to see they must keep trying to form the habit from the very first; and to form the habit they should make the study of specimens the main feature in the course of training."

[Footnote 1: The New Botany. By W.J. Beal. Philadelphia, C.H. Marot, 814 Chestnut St., 1882. Page 5.]

HORSECHESTNUT (_Æsculus Hippocastanum_).

We will begin with the study of a branch of Horsechestnut.[1] The pupils should examine and describe their specimens before discussing them in the class-room. They will need some directions and hints, however, to enable them to work to any advantage. Tell them to open both large and small buds. It is not advisable to study the Horsechestnut bud by cutting sections, as the wool is so dense that the arrangement cannot be seen in this way. The scales should be removed with a knife, one by one, and the number, texture, etc., noted. The leaves and flower-cluster will remain uncovered and will be easy to examine. The gum may be first removed by pressing the bud in a bit of paper. The scholars should study carefully the markings on the stem, in order to explain, if possible, what has caused them. The best way to make clear the meaning of the scars is to show them the relation of the bud to the branch. They must define a bud. Ask them what the bud would have become the next season, if it had been allowed to develop. It would have been a branch, or a part of one. A bud, then, is an undeveloped branch. They can always work out this definition for themselves. Conversely, a branch is a developed bud, or series of buds, and every mark on the branch must correspond to something in the bud. Let them examine the specimens with this idea clearly before their minds. The lesson to prepare should be to write out all they can observe and to make careful drawings of their specimens. Ask them to find a way, if possible, to tell the age of the branch.

[Footnote 1: The pupils should cut their names on their branches and keep them. They will need them constantly for comparison and reference.]

At the recitation, the papers can be read and the points mentioned thoroughly discussed. This will take two lesson-hours, probably, and the drawing may be left, if desired, as the exercise to prepare for the second recitation.

[1]The buds of Horsechestnut contain the plan of the whole growth of the next season. They are scaly and covered, especially towards the apex, with a sticky varnish. The scales are opposite, like the leaves. The outer pairs are wholly brown and leathery, the succeeding ones tipped with brown, wherever exposed, so that the whole bud is covered with a thick coat. The inner scales are green and delicate, and somewhat woolly, especially along the lapping edges. There are about seven pairs of scales. The larger terminal buds have a flower-cluster in the centre, and generally two pairs of leaves; the small buds contain leaves alone, two or three pairs of them. The leaves are densely covered with white wool, to protect them from the sudden changes of winter. The use of the gum is to ward off moisture. The flower-cluster is woolly also.

[Footnote 1: All descriptions are made from specimens examined by me. Other specimens may differ in some points. Plants vary in different situations and localities.]

The scars on the stem are of three kinds, leaf, bud-scale, and flower-cluster scars. The pupils should notice that the buds are always just above the large triangular scars. If they are still in doubt as to the cause of these marks, show them some house-plant with well-developed buds in the axils of the leaves, and ask them to compare the position of these buds with their branches. The buds that spring from the inner angle of the leaf with the stem are _axillary_ buds; those that crown the stems are _terminal_. Since a bud is an undeveloped branch, terminal buds carry, on the axis which they crown, axillary buds give rise to side-shoots. The leaf-scars show the leaf-arrangement and the number of leaves each year. The leaves are opposite and each pair stands over the intervals of the pair below. The same is observed to be true of the scales and leaves of the bud.[1] All these points should be brought out by the actual observation of the specimens by the pupils, with only such hints from the teacher as may be needed to direct their attention aright. The dots on the leaf-scar are the ends of woody bundles (fibro-vascular bundles) which, in autumn, separated from the leaf. By counting these we can tell how many leaflets there were in the leaf, three, five, seven, nine, or occasionally six or eight.

[Footnote 1: Bud-scales are modified leaves and their arrangement is therefore the same as the leaves. This is not mentioned in the study of the Horsechestnut bud, because it cannot be proved to the pupils, but the transition is explained in connection with Lilac, where it may be clearly seen. The scales of the bud of Horsechestnut are considered to be homologous with petioles, by analogy with other members of the same family. In the Sweet Buckeye a series can be made, exhibiting the gradual change from a scale to a compound leaf. See the Botanical Text-Book, Part I, Structural Botany. By Asa Gray. Ivison, Blakeman, Taylor and Co., New York, 1879. Plate 233, p. 116.]

_The Bud Scale-Scars_. These are rings left by the scales of the bud and may be seen in many branches. They are well seen in Horsechestnut. If the pupils have failed to observe that these rings show the position of former buds and mark the growth of successive years, this point must be brought out by skilful questioning. There is a difference in the color of the more recent shoots, and a pupil, when asked how much of his branch grew the preceding season, will be able to answer by observing the change in color. Make him see that this change corresponds with the rings, and he will understand how to tell every year's growth. Then ask what would make the rings in a branch produced from one of his buds, and he can hardly fail to see that the scales would make them. When the scholars understand that the rings mark the year's growth, they can count them and ascertain the age of each branch. The same should be done with each side-shoot. Usually the numbers will be found to agree; that is, all the buds will have the same number of rings between them and the cut end of the branch, but occasionally a bud will remain latent for one or several seasons and then begin its growth, in which case the numbers will not agree; the difference will be the number of years it remained latent. There are always many buds that are not developed. "The undeveloped buds do not necessarily perish, but are ready to be called into action in case the others are checked. When the stronger buds are destroyed, some that would else remain dormant develop in their stead, incited by the abundance of nourishment which the former would have monopolized. In this manner our trees are soon reclothed with verdure, after their tender foliage and branches have been killed by a late vernal frost, or consumed by insects. And buds which have remained latent for several years occasionally shoot forth into branches from the sides of old stems, especially in certain trees."[1]

[Footnote 1: Structural Botany, p. 48.]

The pupils can measure the distance between each set of rings on the main stem, to see on what years it grew best.

_The Flower-Cluster Scars_. These are the round, somewhat concave, scars, found terminating the stem where forking occurs, or seemingly in the axils of branches, on account of one of the forking branches growing more rapidly and stoutly than the other and thus taking the place of the main stem, so that this is apparently continued without interruption. If the pupils have not understood the cause of the flower-cluster scars, show them their position in shoots where they are plainly on the summit of the stem, and tell them to compare this with the arrangement of a large bud. The flower-cluster terminates the axis in the bud, and this scar terminates a branch. When the terminal bud is thus prevented from continuing its growth, the nearest axillary buds are developed.[1] One shoot usually gets the start, and becomes so much stronger that it throws the other to one side. The tendency of the Horsechestnut to have its growth carried on by the terminal buds is so strong that I almost feel inclined to say that vigorous branches are never formed from axillary buds, in old trees, except where the terminal bud has been prevented from continuing the branch. This tendency gives to the tree its characteristic size of trunk and branches, and lack of delicate spray. On looking closely at the branches also, they will be seen to be quite irregular, wherever there has been a flower-cluster swerving to one side or the other.

[Footnote 1: The first winter that I examined Horsechestnut buds I found, in many cases, that the axillary shoots had from a quarter of an inch to an inch of wood before the first set of rings. I could not imagine what had formed this wood, and it remained a complete puzzle to me until the following spring, when I found in the expanding shoots, that, wherever a flower-cluster was present, there were one or two pairs of leaflets already well developed in the axils, and that the next season's buds were forming between them, while the internodes of these leaflets were making quite a rapid growth. Subsequently, I found the leaflets also in the buds themselves. I found these leaflets developed on the tree only in the shoots containing flower-clusters, where they would be needed for the future growth of the branches. I suppose the reason must be that the flower-cluster does not use all the nourishment provided and that therefore the axillary buds are able to develop. It would be interesting to know what determines the stronger growth of the one which eventually becomes the leader.]

There is one thing more the pupils may have noticed. The small round dots all over the young stem, which become long rifts in the older parts, are breaks in the epidermis, or skin of the stem, through which the inner layers of bark protrude. They are called lenticels. They provide a passage for gases in and out of the stem. In some trees, as the Birch, they are very noticeable.

After discussing the subject thoroughly in the class-room, the pupils should rewrite their papers, and finally answer the following questions, as a species of review. I have thus spent three recitations on the Horsechestnut. The work is all so new, and, if properly presented, so interesting, that a good deal of time is required to exhaust its possibilities of instruction. If the teacher finds his scholars wearying, however, he can leave as many of the details as he pleases to be treated in connection with other branches.

QUESTIONS ON THE HORSECHESTNUT.

How many scales are there in the buds you have examined?

How are they arranged?

How many leaves are there in the buds?

How are they arranged?

Where does the flower-cluster come in the bud?

Do all the buds contain flower-clusters?

What is the use of the wool and the gum?

Where do the buds come on the stem?

Which are the strongest?

How are the leaves arranged on the stem?

Do the pairs stand directly over each other?

What are the dots on the leaf-scars?

How old is your branch?

How old is each twig?

Which years were the best for growth?

Where were the former flower-clusters?

What happens when a branch is stopped in its growth by flowering?

What effect does this have on the appearance of the tree?

In some parts of the country the Horsechestnut is not so commonly planted as in New England. In the southern states the Magnolia may be used in its stead, but it is not nearly so simple an example of the main points to be observed.[1]

[Footnote 1: Reader in Botany. VII. Trees in Winter.]

MAGNOLIA UMBRELLA.

The bud may be examined by removing the scales with a knife, as in Horsechestnut, and also by cutting sections. The outer scales enfold the whole bud, and each succeeding pair cover all within. They are joined, and it is frequently difficult to tell where the suture is, though it can generally be traced at the apex of the bud. On the back is a thick stalk, which is the base of the leaf-stalk. Remove the scales by cutting carefully through a single pair, opposite the leaf-stalk, and peeling them off. The scales are modified stipules, instead of leaf-stalks, as in Horsechestnut. The outer pair are brown and thick, the inner green, and becoming more delicate and crumpled as we proceed toward the centre of the bud. The leaves begin with the second or third pair of scales. The first one or two are imperfect, being small, brown, and dry. The leaves grow larger towards the centre of the bud. They are covered with short, silky hairs, and are folded lengthwise, with the inner surface within (_conduplicate_). In the specimens I have examined I do not see much difference in size between the buds with flowers and those without. In every bud examined which contained a flower, there was an axillary bud in the axil of the last, or next to the last, leaf. This bud is to continue the interrupted branch in the same way as in Horsechestnut.

There are from six to ten good leaves, in the buds that I have seen. Those without flowers contain more leaves, as in Horsechestnut. In the centre of these buds the leaves are small and undeveloped. The flower is very easy to examine, the floral envelopes, stamens and pistils, being plainly discernible. The bud may also be studied in cross-section. This shows the whole arrangement. The plan is not so simple as in Horsechestnut, where the leaves are opposite. The subject of leaf-arrangement should be passed over until phyllotaxy is taken up.

The scars on the stem differ from Horsechestnut in having no distinct bands of rings. The scales, being stipules, leave a line on each side of the leaf-scar, and these are separated by the growth of the internodes. In the Beech, the scales are also stipules; but, whereas in the Magnolia there are only one or two abortive leaves, in the Beech there are eight or nine pairs of stipules without any leaves at all. The rings thus become separated in Magnolia, while in the Beech the first internodes are not developed, leaving a distinct band of rings, to mark the season's growth. The Magnolia is therefore less desirable to begin upon. The branches are swollen at the beginning of a new growth, and have a number of leaf-scars crowded closely together. The leaf-scars are roundish, the lower line more curved. They have many dots on them. From each leaf-scar runs an irregular line around the stem. This has been left by the stipules.

The flower-scar is on the summit of the axis, and often apparently in the axil of a branch, as in Horsechestnut. Sometimes the nearest axillary bud is developed; sometimes there are two, when the branch forks. The axillary buds seldom grow unless the terminal bud is interrupted. The tree therefore has no fine spray.

LILAC _(Syringa vulgaris_).

Ask the scholars to write a description of their branches and to compare them with Horsechestnut. These papers should be prepared before coming into the class, as before.

The buds are four-sided. The scales and leaves are opposite, as in Horsechestnut. The outer pair sometimes have buds in their axils. Remove the scales one by one with a knife, or better, with a stout needle. The scales gradually become thinner as we proceed, and pass into leaves, so that we cannot tell where the scales end and leaves begin. After about six pairs are removed, we come, in the larger buds, to leaves with axillary flower-clusters. The leaves grow smaller and the flower-clusters larger till we come to the centre, where the axis is terminated by a flower-cluster. There is a great difference in the buds on different bushes and on shoots of the same bush, some being large, green, and easy to examine, others small, hard, and dark-colored. It is better, of course, to select as soft and large buds as possible for examination.

That the scales are modified leaves is plainly shown by the gradual transition they undergo, and also by the fact that buds are developed in their axils. If any of these can be shown to the pupils, remind them of the experiment where the top of a seedling Pea was cut off and buds forced to develop in the axils of the lower scales.[1] The transition from scales to leaves can be well studied by bringing branches into the house, where they will develop in water, and towards spring may even be made to blossom. Cherry, Apple, Forsythia, and other blossoming trees and shrubs can be thus forced to bloom. Place the branches in hot water, and cut off a little of their ends under water. If the water is changed every day, and the glass kept near the register or stove, they will blossom out very quickly. These expanded shoots may be compared with the buds. The number of leaves in the bud varies.

[Footnote 1: See p. 31.]

The leaf-scars of Lilac are horseshoe-shaped and somewhat swollen. It can often be plainly seen that the outer tissue of the stem runs up into the scar. It looks as if there were a layer of bark, ending with the scar, fastened over each side of the stem. These apparent layers alternate as well as the scars. The epidermis, or skin of the leaves, is in fact always continuous with that of the stem. There are no dots on the leaf-scars.

The rings are not nearly so noticeable as in Horsechestnut, but they can be counted for some years back.

The flower-cluster can often be traced by a dried bit of stem remaining on the branch.

The terminal bud in the Lilac does not usually develop, and the two uppermost axillary buds take its place, giving to the shrub the forked character of its branching. In all these bud studies, the pupil should finish by showing how the arrangement of the buds determines the growth of the branches.

QUESTIONS ON THE LILAC.

How do the scales differ from those of Horsechestnut?

How many scales and leaves are there?

How are they arranged?

Where does the flower-cluster come in the bud?

Do all the buds contain flower-clusters?

How does the arrangement of leaves and flower-clusters differ from that of Horsechestnut?

How old is your branch?

Which buds develop most frequently?

How does this affect the appearance of the shrub?

COPPER BEECH (_Fagus sylvatica, var. purpurea_).

The buds are long and tapering, the scales thin and scarious, the outer naked, the inner with long, silky hairs. Remove the scales one by one, as in Lilac. The outer four or six pairs are so minute that the arrangement is not very clear, but as we proceed we perceive that the scales are in alternate pairs, as in Horsechestnut; that is, that two scales are exactly on the same plane. But we have learned in the Lilac that the scales are modified leaves, and follow the leaf-arrangement of the species. The Beech is alternate-leaved, and we should therefore expect the scales to alternate. The explanation is found as we go on removing the scales. At the eighth or ninth pair we come upon a tiny, silky leaf, directly between the pair of scales, and, removing these, another larger leaf, opposite the first but higher up on the rudimentary stem, and so on, with the rest of the bud. There are five or more leaves, each placed between a pair of scales. Our knowledge of the parts of a leaf shows us at once that the scales must be modified stipules, and that therefore they must be in pairs.[1] Other examples of scales homologous with stipules are the American Elm, Tulip-tree, Poplar and Magnolia. The leaves are plaited on the veins and covered with long, silky hairs. The venation is very distinct. The outer leaves are smaller and, on examining the branch, it will be seen that their internodes do not make so large a growth as the leaves in the centre of the bud.

[Footnote 1: See the stipules of the Pea, p. 31.]

The leaf-scars are small, soon becoming merely ridges running half round the stem.

The bud-rings are very plain and easily counted. For this reason, and because it branches freely, it is a good tree for measurements of growth, as is seen in the following tables. Nos. 1, 2, 3 and 4: were made by a class of girls, from fourteen to sixteen, from a tree on my lawn. No. 5 was made by a pupil, whom I taught by correspondence, from a tree of the same species in another town. No. 6 was made by myself from my own tree. The measurements of the first four tables were somewhat revised by me, as they were not perfectly accurate. The pupils should always be cautioned to measure from the beginning of one set of rings to the beginning of the next.[1]

[Footnote 1: Care must be taken to select branches well exposed to the light. Of course there are many circumstances that may aid or hinder the growth of any particular branch.]

NO. 1.

YEARS. GROWTH OF 1ST BRANCH. 2nd BRANCH. 3RD BRANCH 4TH BRANCH. MAIN AXIS. ---------------------------------------------------------------- in. '79 8-1/2 -- -- -- -- '80 4-1/2 2 1-7/8 -- -- '81 3-1/2 1-1/8 2-5/8 -- -- '82 6 5/8 4-1/4 5-7/8 -- '83 7-3/8 3-3/8 5-1/4 4 5-3/4 '84 2 1/2 3/4 3/8 5-3/8 '85 5/8 1/4 3/8 1/2 1 '86 5-5/8 7/8 4-3/8 3-1/8 5

NO. 2.

YEARS. GROWTH of 1ST 2nd 3RD 4TH 5TH MAIN AXIS. BRANCH BRANCH BRANCH BRANCH BRANCH ---------------------------------------------------------------- in. '79 8 -- -- -- -- -- -- '80 3-1/2 5-1/4 5-1/2 5-5/8 -- -- -- '81 4-3/4 3/4 1/2 2-1/2 2 -- -- '82 5-3/4 7/8 2 3/4 3/8 1/2 -- '83 5-1/4 4-3/4 5-1/2 4 3-1/4 2-3/8 1-3/4 -- '84 1/2 1 3/4 3/8 1 3/4 1 3/8 '85 2-3/4 1-3/4 4-3/8 3/4 3/4 2-1/8 3-1/4 1-1/4 '86 7-1/2 5-1/2 6-3/4 3 3 4-1/2 3-1/8 5

NO. 3.

YEARS. GROWTH of 1ST 2nd 3RD 4TH 5TH MAIN AXIS. BRANCH BRANCH BRANCH BRANCH BRANCH ----------------------------------------------------- in. '80 8-1/4 -- -- -- -- -- '81 4-1/2 3-1/2 3-3/4 -- -- -- '82 5-1/2 3/4 1-1/2 1 -- -- '83 3-1/4 3-3/4 4-1/2 3/4 2 1-1/4 '84 5-1/2 1/2 3/4 1 1/2 3 '85 1/2 1-3/4 1/2 3/8 1 1/2 '86 4-1/4 3-3/8 2-3/8 1-1/4 2-1/4 1-1/2

NO. 4.

YEARS GROWTH 1ST 2nd 3RD 4TH of MAIN BRANCH BRANCH BRANCH BRANCH AXIS ----------------------------------------- in. '81 7-3/4 -- -- -- -- '82 8-3/4 6 6 -- -- '83 6-3/4 5-1/4 4 4-3/4 5-1/2 '84 4-1/2 5/8 1-5/8 2-1/4 3-1/4 '85 2 5/8 3/16 2 3/4 '86 10-3/4 1-3/4 1/4 7-1/4 3-1/2

NO. 4. (cont.)

YEARS 5TH 6TH 7TH 8TH 9TH BRANCH BRANCH BRANCH BRANCH BRANCH ----------------------------------- in. '81 -- -- -- -- -- '82 -- -- -- -- -- '83 -- -- -- -- -- '84 3/4 2-1/2 -- -- -- '85 7/8 5/8 1/4 3/4 -- '86 4-3/4 6-3/8 1 2-1/4 6-1/2

NO. 5.

YEARS GROWTH 1ST 2nd 3RD 4TH 5TH 6TH of MAIN BRANCH BRANCH BRANCH BRANCH BRANCH BRANCH AXIS ----------------------------------------------------- in. '82 6-7/8 --- --- --- --- --- --- '83 6-1/2 4-3/4 4-1/4 --- --- --- --- '84 4-3/4 1/4 1-3/4 3-1/2 --- --- --- '85 4-1/2 3/4 1 2-3/4 2-3/4 --- --- '86 6-1/4 2-1/4 4-3/4 6-3/4 2-3/4 5-3/4 --- '87 6-3/4 1-1/8 3-1/4 4 2-1/4 3 5-1/2

NO. 6.

YEARS MAIN 1ST 2ND 2ND 2ND 3RD 4TH AXIS BRANCH BRANCH BRANCH BRANCH BRANCH BRANCH ----------------------------------------------------- in. 1st 2nd side side '80 6-1/4 --- --- shoot. shoot. --- --- '81 8-3/4 6-3/4 --- --- --- --- --- '82 8-1/2 6-1/4 6-7/8 --- --- --- . '83 4-3/4 1-1/2 2-3/8 --- --- 4 . '84 3-1/2 3-1/8 5-1/8 --- --- 1-3/4 7/8 '85 4-1/2 3/8 4-3/4 2-1/4 --- 6 1 '86 6+ 6-3/4 12-1/8 5-1/2 10-1/2 8-7/8 5-1/8 '87 bough 2-1/2 8-3/4 4-1/4 4-1/4 4-6/8 3-3/4 broken.

One question brought up by these measurements is whether there is any correspondence in growth between the main axis and its branches. It appears in these tables that there is a general correspondence, in this tree at least. In the recitation of the class, whose tables are given above (Nos. 1, 2, 3 and 4), we took all the measurements of these four branches for the year 1885 and added them. We did the same for 1886, and compared the results. The total growth for 1885 was 31-15/16 inches; for 1886, leaving out the measurement of the twig whose entire growth was in that year, 109-3/4 inches or nearly 3-1/2 times as much. The proportion held in a general way throughout, there being only a single case of a branch where the growth was greater in the first year.[1] But there is a point that must not be overlooked in this connection. The branches of the Beech seem to grow about equally well in the first, second, third, or any succeeding year. In some trees, as the Ash, the axillary buds make a large growth, and the succeeding terminal buds carry on the branch much more slowly; in other trees, as the Cherry, a branch grows very slowly in the first few years and then suddenly takes a start. These facts would appear in tables of growth, made from branches of these trees, but the addition of results for any particular year would have no significance.

[Footnote 1: The spring of 1880 was a remarkably early one. Thus I find in my diary of that year the following entries:--

April 17. The red maples are in full bloom, the elms almost over. The leaves of the Horsechestnut are quite large. The lilacs are nearly in leaf. April 24. We went up to Waverley and found bloodroot up, spice bush out, violets, dog-tooths and anemones, also caltha. April 28. All the cherries are in full bloom. April 29. Picked an apple blossom in bud, beautifully pink.

The season was nearly three weeks earlier than usual. 1885 on the other hand was a late spring.]

In table No. 5, the addition of the measurements for 1885 and 1886 shows the growth in the latter year to be about twice that of the former. This branch came from a tree in another town. We have tried also to discover whether the number of leaves each year has any relation to growth. I cannot see that it has, but it requires many experiments to determine these points. To study this, make tables of the number of leaves on the branch each year. I think teachers would find it interesting to keep all data of this kind of work done by their classes, with a view to tabulation and comparison. The scholars themselves are exceedingly interested in anything that partakes of the nature of an original investigation.[1]

[Footnote 1: The class, previously mentioned, were much interested in the addition of their results. One of them asked me whether this subject of measurements had been treated in any book. I replied that I had never seen it mentioned. My attention was afterwards called to "What may be learned from a Tree," by Prof. Harlan Couitas. D. Appleton & Co., New York, 1863. I found, greatly to my surprise, that he had not only given diagrams of growth, but that he also had selected a Copper Beech as his example.]

The leaf-arrangement of the Beech is alternate, on the one-half plan. The small twigs turn upwards, so that all the spray is on the upper side, giving a flat appearance to the branch.[1] This gives the leaves a better exposure to the light. Both the terminal and axillary buds grow freely, thus forming long, straight limbs, with many branches and much fine spray.

[Footnote 1: Phyllotaxy is treated later, by a comparison and study of many branches, but the teacher can draw the pupils' attention to the fact that each Beech leaf and twig is on exactly the opposite side of the branch from the preceding one. This allows all the twigs to grow towards one side of the branch, whereas in trees on the two-fifths plan, as the Apple, Poplar, Oak, etc., no such regularity would be possible, on account of their many different angles with the stem.]

The bark of the Beech is beautifully smooth. The extreme straightness of the trunk and limbs is very striking, and may be compared to the crooked limbs of the Horsechestnut, where the branch is continually interrupted by the flower-cluster. In the Beech the flowers are axillary.

QUESTIONS ON THE BEECH.

How are the scales of the Beech bud arranged?

How many leaves are there in the bud?

How does the arrangement of the scales and leaves in the bud differ from that of the Horsechestnut?

How are the leaves folded in the bud?

What is the arrangement of the leaves on the stem?

How does this differ from Horsechestnut and Lilac?

How old is your branch?

How old is each twig?

What years were the best for growth?

How does the growth of the branches differ from that of Horsechestnut? From Lilac?

Explain these differences with reference to the growth and arrangement of the buds?

In what direction do the twigs grow?

How does this affect the appearance of the tree?

Compare the amount of spray of the Beech and Horsechestnut and explain the reason of the difference.

These questions are only intended for review, they are never to be used for the first study of the specimen.

AMERICAN ELM (_Ulmus Americana_).

The buds are covered with brown scales, which are hairy on the edges. The flower-buds are larger than the leaf-buds and are in the axils of the lower leaves of the preceding year. Each leaf in the bud is enclosed by a pair of scales. They are so small that the pupils, unused to delicate work, will hardly discover them. Under a glass they can be seen to be ovate, folded on the midrib with the inner face within (_conduplicate_), and with an ovate scale joined to the base of the leaf on either side. The scales thus show themselves to be modified stipules. The venation of the leaves is very plain. The scales are much larger than the leaves. The flower-buds contain a cluster of flowers, on slender green pedicels. The calyx is bell-shaped, unequal, and lobed. The stamens and pistil can be seen. The flower-clusters do not seem to leave any mark which is distinguishable from the leaf-scar.

The leaf-scars are small and extend about half around the stem. The arrangement is alternate on the one-half plan. There are three dots on the scar.

The rings are quite plain. The tree can be used to make tables of growth, like those of the Beech.

The buds will probably be too small for examination by the pupils, at present, but their position and development can be studied, and are very instructive. As the leaf-buds are all on the ends of the branchlets, the twigs and branches will be just below the bud-rings, and then there will be a space where no twigs nor branches will be found, till the next set of rings is reached. This gives the branches more room to develop symmetrically. The terminal buds do not develop in the Elm, in old trees, the bud axillary to the last leaf of the season taking its place, and most of the other axillary buds growing also. This makes the tree break out into very fine spray. A tree like the Elm, where the trunk becomes lost in the branches, is called _deliquescent_; when the trunk is continued to the top of the tree, as in the Spruce, it is _excurrent_.

The small, feathery twigs and branches that are often seen on the trunks and great limbs of the elm grow from buds which are produced anywhere on the surface of the wood. Such buds are called _adventitious_ buds. They often spring from a tree when it is wounded.

"The American elm is, in most parts of the state, the most magnificent tree to be seen. From a root, which, in old trees, spreads much above the surface of the ground, the trunk rises to a considerable height in a single stem. Here it usually divides into two or three principal branches, which go off by a gradual and easy curve. Theses stretch upwards and outwards with an airy sweep, become horizontal, the extreme half of the limb, pendent, forming a light and regular arch. This graceful curvature, and absence of all abruptness, in the primary limbs and forks, and all the subsequent divisions, are entirely characteristic of the tree, and enable an observer to distinguish it in the winter and even by night, when standing in relief against the sky, as far as it can be distinctly seen."[1]

[Footnote 1: A Report on the Trees and Shrubs growing naturally in the Forests of Massachusetts. By Geo. B. Emerson, Boston, Little, Brown and Co., 1875.

This book will be found very useful, containing careful descriptions of many trees and shrubs, and interesting facts about them.]

QUESTIONS ON THE AMERICAN ELM.

How do the flower-buds differ from the leaf-buds in position and appearance?

What is the arrangement of the leaves?

What other tree that you have studied has this arrangement?

How old is your branch?

Where would you look to see if the flower-cluster had left any mark?

Why is it that several twigs grow near each other, and that then comes a space without any branches?

What buds develop most frequently?

How does this affect the appearance of the tree?

What is a tree called when the trunk is lost in the branches?

BALM OF GILEAD (_Populus balsamifera, var. candicans_).

The buds are pointed: the terminal slightly angled, the axillary flattened against the stem.[1] Some of the axillary buds contain leaves and some flowers; the appearance of the leaf-buds and flower-buds being the same. The scales of the bud are modified stipules. The terminal buds have about three pairs of the outer scales brown and leathery. The inner scales, as well as the leaves, are coated with resinous matter, which has a strong odor and a nauseous taste. The smaller outer scales have no corresponding leaf, and apparently are modified stipules of the leaves of the preceding year, but the larger ones have a leaf to each pair of scales. The outer and inner leaves are small, the middle ones larger. Comparing the branch, it will be seen that these leaves make the largest growth of internode. The leaves are rolled towards the midrib on the upper face (_involute_). There are about ten which are easily seen and counted, the inner ones being very small, with minute scales. The axillary buds have a short thick scale on the outer part of the bud, then about three pairs of large scales, each succeeding one enwrapping those within, the outer one brown and leathery. The scales of the flower-buds are somewhat gummy, but not nearly so much so as those of the leaf-buds. Within is the catkin. Each pistil, or stamen (they are on separate trees, _dioecious_) is in a little cup and covered by a scale, which is cut and fringed.

[Footnote 1: These buds cannot be satisfactorily examined in cross section, on account of the resin. The scales must be removed one by one, with a knife, with a complete disregard of the effect upon the hands.]

The leaf-scars are somewhat three-lobed on the young parts, with three dots, indicating the fibro-vascular bundles, which ran up into the leaf. The scars are swollen, making the young branches exceedingly rough. In the older parts the scars become less noticeable. Strong young shoots, especially those which come up from the root, are strongly angled, with three ridges running up into each leaf-scar, making them almost club-shaped. There are often from twenty to thirty leaves in one year's growth, in such shoots, and all the leaves are not rudimentary in the bud. The growth in this case is said to be _indefinite_. Usually in trees with scaly buds the plan of the whole year's growth is laid down in the bud, and the term _definite_ is applied. Branches, like the Rose, that go on growing all summer grow indefinitely.

The bud-scale scar is quite different from the other trees which we have examined. It is not composed of definite rings, but of leaf-scars with long ridges running from each side of them, showing the scales to be modified stipules. The leaf-scars have become somewhat separated by the growth of the internodes. In the Beech, there are eight, or more, pairs of scales with no leaves, so that the internodes do not develop, and a ring is left on the branch.

The flower-cluster leaves a concave, semicircular scar, in the leaf-axil.

The terminal buds are the strongest and not very many axillary buds develop, so that the tree has not fine spray.

The leaf-arrangement is alternate, on the 2/5 plan. Phyllotaxy is not yet to be taken up, but the pupils should be shown the different angles of the branching of the twigs, and told to compare them with Beech and Elm.

QUESTIONS ON THE BALM OF GILEAD.

In which buds are the flower-clusters?

Are there flowers and leaves in the same buds?

What are the scales of the bud?

How are the leaves folded in the bud?

How do the axillary and terminal buds differ?

What are the dots on the leaf-scars?

Why is there no distinct band of rings as in Beech?

How old is your branch?

Where do you look for flower-cluster scars?

Which buds are the strongest?

How does this affect the appearance of the tree?

What makes the ends of the branches so rough?

Compare the arrangement of the twigs and branches with Beech and Elm, with Horsechestnut and Lilac.

TULIP-TREE (_Liriodendron Tulipifera_).

The buds are small, flat, and rounded at the apex. They are sheathed by scales, each leaf being covered by a pair, whose edges cohere. The outer pair are brown and are the stipules of the last leaf of the preceding year. The leaves are conduplicate, as in Magnolia, and have the blade bent inwards on the petiole (_inflexed_). Their shape is very clearly to be seen, and no bud is more interesting in the closeness of its packing. Axillary buds are often found within. The flowers grow high upon the trees and towards the ends of the branches.

The leaf-scars are round with many dots. The scar of the stipules is a continuous line around the stem, as in Magnolia.

CHERRY _(Prunus Cerasus_).

The leaf-buds are terminal, or in the axils of the upper leaves of the preceding year; the flower buds are axillary. There is but one bud in each axil, and usually two or three flowers in each bud, but the leaves on the twigs are crowded and the flowers therefore appear in clusters. The blossom-buds are larger and more rounded than the leaf-buds.

The buds of the tree develop very easily in the house, and as they are so small they can be better studied in watching them come out, than by attempting to dissect them, unless the scholars are sufficiently advanced to use the microscope easily. It is always bad for a pupil to attempt to describe what he sees but imperfectly. He will be sure to jump at any conclusions which he thinks ought to be correct.

The leaf-scars are semicircular, small and swollen.

The bud-rings are plain. The twigs make a very small growth in a season, so that the leaf-scars and rings make them exceedingly rough.

The flower-cluster scars are small circles, with a dot in the centre, in the leaf-axils. The flowers come before the leaves.

The leaf-arrangement is alternate on the 2/5 plan. The pupils may compare the branching with that of their other specimens.

RED MAPLE (_Acer rubrum_).

This is a good specimen for the study of accessory buds. There is usually a bud in the axil of each lower scale of the axillary buds, making three side by side. We have already noticed this as occurring sometimes in Lilac. It is habitually the case with the Red Maple. The middle bud, which is smaller and develops later, is a leaf-bud. The others are flower-buds.

The leaf-scars are small, with three dots on each scar. The rings are very plain. The flower-cluster leaves a round scar in the leaf-axil, as in Cherry.

The leaves are opposite and the tree branches freely. The twigs seem to be found just below the bud-rings, as the upper leaf-buds usually develop best and the lower buds are single, containing flowers only.

NORWAY SPRUCE (_Picea excelsa_).

The buds are terminal, and axillary, from the axils of the leaves of the preceding year, usually from those at the ends of the branchlets. They are covered with brown scales and contain many leaves.

The leaves are needle-shaped and short.[1] They are arranged densely on the branches, alternately on the 8/21 plan (see section on phyllotaxy). When they drop off they leave a hard, blunt projection which makes the stem very rough. As the terminal bud always develops unless injured, the tree is excurrent, forming a straight trunk, throwing out branches on every side. The axillary buds develop near the ends of the branchlets, forming apparent whorls of branches around the trunk. In the smaller branches, as the tree grows older, the tendency is for only two buds to develop nearly opposite each other, forming a symmetrical branch.

[Footnote 1: The pupils should observe how much more crowded the leaves are than in the other trees they have studied. The leaves being smaller, it is necessary to have more of them. Large-leaved trees have longer internodes than those with small leaves.]

The bud-scales are persistent on the branches and the growth from year to year can be traced a long way back.

The cones hang on the ends of the upper branches. They are much larger than in our native species of Black and White Spruce.

The Evergreens are a very interesting study and an excellent exercise in morphology for the older scholars.

2. _Vernation_. This term signifies the disposition of leaves in the bud, either in respect to the way in which each leaf is folded, or to the manner in which the leaves are arranged with reference to each other. The pupils have described the folding of the leaves in some of their specimens.

In the Beech, the leaf is _plicate_, or plaited on the veins. In the Elm, Magnolia, and Tulip-tree, it is _conduplicate_, that is, folded on the midrib with the inner face within. In the Tulip-tree, it is also _inflexed_, the blade bent forwards on the petiole. In the Balm of Gilead, the leaf is _involute_, rolled towards the midrib on the upper face.

Other kinds of vernation are _revolute_, the opposite of involute, where the leaf is rolled backwards towards the midrib; _circinate_, rolled from the apex downwards, as we see in ferns; and _corrugate_, when the leaf is crumpled in the bud.

In all the trees we have studied, the leaves simply succeed each other, each leaf, or pair of leaves, overlapping the next in order. The names of the overlapping of the leaves among themselves, _imbricated, convolute, etc_., will not be treated here, as they are not needed. They will come under _æstivation_, the term used to describe the overlapping of the modified leaves, which make up the flower.[1]

[Footnote 1: Reader in Botany. VIII. Young and Old Leaves.]

3. _Phyllotaxy_. The subject of leaf-arrangement is an extremely difficult one, and it is best, even with the older pupils, to touch it lightly. The point to be especially brought out is the disposition of the leaves so that each can get the benefit of the light. This can be seen in any plant and there are many ways in which the desired result is brought about. The chief way is the distribution of the leaves about the stem, and this is well studied from the leaf-scars.

The scholars should keep the branches they have studied. It is well to have them marked with the respective names, that the teacher may examine and return them without fear of mistakes.