Outlines of Lessons in Botany Part 7

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 cla.s.s, 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 cla.s.ses, 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 cla.s.s, 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-cl.u.s.ter. 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 gla.s.s 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 cl.u.s.ter of flowers, on slender green pedicels. The calyx is bell-shaped, unequal, and lobed. The stamens and pistil can be seen. The flower-cl.u.s.ters do not seem to leave any mark which is distinguishable from the leaf-scar.

[Ill.u.s.tration: FIG. 16.--American Elm. 1. Branch in winter state: _a_, leaf-scars; _b_, bud-scars; _d_, leaf-buds; _e_, flower-buds. 2. Branch, with staminate flower-buds expanding. 3. Same, more advanced. 4. Branch, with pistillate flowers, the leaf-bud also expanding.]

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 s.p.a.ce 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 _advent.i.tious_ 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 princ.i.p.al 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 Ma.s.sachusetts. 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?