"388. The Growth of the Plantlet when it springs from the seed, is only a continuation of the same process. The bladder-like cells of which the embryo consists, multiply in number by the repeated division of each cell into two. And the plant-let is merely the aggregation of a vastly larger number of these cells. This may be clearly ascertained by magnifying any part of a young plantlet. The young root, being more transparent than the rest, answers the purpose best. Figs. 11 and 12 are two small bits of the surface highly magnified, showing the cells. And if we make a thin slice through the young root both lengthwise and crosswise, and view it under a good microscope (Fig. 13), we may perceive that the whole interior is made up of just such cells. It is essentially the same in the fell-grown herb and the tree.

"389. So the plant is an aggregation of countless millions of little vesicles, or cells (Fig. 13), aa they are called, essentially like the cell it began with in the formation of the embryo (Fig. 3); and this first cell is the foundation of the whole structure, or the ancestor of all the rest. And a plant is a kind of structure, built up of these individual cells, something as a house is built of bricks - only the bricks or cells are not brought to the forming plant, but are made in it and by it; or, to give a better comparison, the plant is constructed much as a honeycomb is built up of cells - only the plant constructs itself, and shapes its own materials into fitting forms.

"390. And vegetable growth consists of two things: 1st, the expansion of each cell until it gets its full size (which is commonly not more than 1/400 of an inch in diameter);and 2d, the multiplication of the cells in number. It is by the latter, of course, the principal increase of plants in bulk takes place".

Fig. 11.

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Fig. 12.

Tissue from the rootlet of a seedling Maple, magnified, showing root hairs.

Fig. 11. - Tissue from the rootlet of a seedling Maple, magnified, showing root-hairs. Fig. 12. - A small portion, more magnified.

Fig. 13.

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Fig. 14.

One cell, like these of Fig. 14, detached.

Fig, 13. - One cell, like these of Fig. 14, detached. Fig. 14. - View of a little cellular tissue of a rootlet, cat crosswise and lengthwise.

[We trespass on the next Lesson, to make the illustration still more complete].

398. Cellular Tissue

The cells, as they multiply, build up the tissues or ' fabric of the plant, which may be likened to a wall or an edifice built of bricks, or, still better, to a honeycomb composed of ranges of cells (Fig. 14).

"394. The walls of the cells are united where they touch each other, and so the partition appears to be a simple membrane, although it is really double; as may be shown by boiling the tissue a few minutes, and then pulling the parts asunder. And in soft fruits the cells separate in ripening, although they were perfectly united into a tissue, when green, like that of Fig. 14.

"395. In that figure, the cells fit together perfectly, leaving no interstices, except a very small space at some of the corners. Dot in most leaves, the cells are loosely heaped together, leavtng spaces or passages of all sizes; and in the leaves and stems of aquatic and marsh plants, in particular, the cells are built up into narrow partitions, which form the sides of large and regular canals or passages (aa shown in Fig. 15).

These passages form the holes ot cavities so conspicuous on cutting across any of these plants, and which are always filled with air. They may be likened to a stack of chimneys, built up of cells in place of bricks".

An ordinary size of cell is from 1/300 to 1/500 of an inch; so that there may generally be from twenty-seven to one hundred and twenty-five millions of cells in the compass of a cubic inch! Over twenty thousand millions of cells must be formed in a day in the flower stems of the century plant, which grow at the rate of a foot in twenty-four hoard, and become about six inches in diamter.

[Gould anything be more lacid or intelligible? And what is singular, it is new. Vegetable anatomy began with Malpighi and Grew, who arrived at very good views of structure, better than their successors down to forty years ago, or thereabouts. But as to production of cells, or growth by the cell, our present knowledge was opened up by Germans, and more is owing to one still living, and not old (viz: Van Mohl, of Tdbiugen), than to any one else. He began to publish aboot twenty-five years ago.

Only within the last half-dozen years, however, has it been possible to give a simple and clear account like the above of vegetable growth, all based on thoroughly verified investigations. In this we owe most to Mohl, Schleiden (and earlier, to Mirbel), not to mention a host of very recent vegetable anatomists. In England, it is principally Lindley and Henfrey who have put this knowledge into available shape for English readers; on these Dr. Gray is a decided improvement, in the clearness and brevity with which he declares the new truths. - Ed].

Fig. 15.

Part of a slice across the stem of the Cella Althlopices, magnifield.

Fig. 15. - Part of a slice across the stem of the Cella Althlopices, magnifield.

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How Plants Grow #1

On other pages will be found Dr. Gray's exposition of " How Plants Grow," to which we particularly invite attention, as the result of verified science, and as of great interest to all. To employ a simple illustration of this knowledge: a few years since, men were puzsled to know how it was that grafts do not produce the same fruit as the stock - why, for instance, the root of one pear-tree may supply juices of twenty or more kinds. The discoveries of modern vegetable physiology disclose the successive growths of cells, each upon its predecessor, and each successor taking the exact character, and elaborating with the aid of its leaves, each its own peculiar juices. The improvements in the microscope have aided these researches, and we now have access to one of the great secrets of nature which our ancestors knew nothing about. Dr. Gray's illustrations have reminded us of the following lines: -

"Instinct with life, the buried teed now shoots On earth's cold bosom its descending roots; With what elastic arms its rising stem Parts the twin lobes, expands the throbbing gem. Soon in bright veins the silvery sap ascends, And reflaent blood in milky eddies bends; Till spread in air, the leaves respiring play, And drink the golden quintessence of the day".