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Page:Popular Science Monthly Volume 21.djvu/302

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THE POPULAR SCIENCE MONTHLY.

the study of the cells of growing plants. It becomes, then, a matter of some interest to know something about these cells; and, if the reader can imagine himself for a little while looking through the lenses of our microscope, it will be the purpose of this article to tell him some little of what he may see while he studies the cells of plants.

We may begin with the simplest form of plant-cells; and so, for our first experiment, let us examine a drop of brewer's yeast. Here (Fig. 1) are the cells of the famous yeast-plant, the cells which are the active agents wherever yeast is employed, whether in the beer-vat or PSM V21 D302 Yeast cells.jpgFig. 1.—Yeast-Cells. batter-crock. In both cases we find the cells producing fermentation: desirable in beer for the sake of the alcohol resulting; in bread, for the carbonic gas set free in form of bubbles, which, permeating the dough, make it spongy and light. But look at the shape of these cells. Little oval bodies they are, some almost round. Many are entirely isolated, so that we see a single cell may constitute the entire plant; some are linked together, as links in a chain. The attachment here, however, is not very intimate, when once the cells have attained their full size, for then each cell readily and naturally parts company with its neighbor parent, I should rather say, for the cells, as they adhere together, represent really so many successive generations, and illustrate for us one method of cell-multiplication, namely, that which is effected by budding. New cells are continually pushed out as buds on the sides of cells already in existence. The buds grow, reach maturity very rapidly, and in a very short time themselves give rise to new buds and cells. These little yeast-cells, which are not more than three or four ten-thousandths of an inch in diameter at most, are about as simple vegetable cells as we may find anywhere. Growing thus isolated from each other, hardly so much as jostling one another in life's race, there seems no reason why such cells should not be perfectly spherical, or why, so to speak, life's work should not, with them, result in a well-rounded whole.

But the yeast-plant belongs low down in the scale of life, and its simplicity of cell-structure corresponds well with its rank. For the greatest variety of form among plant-cells we must look to higher plants, though not to the highest. The Algæ, in their marine forms well known to every gatherer of "sea-moss," and in fresh-water forms familiar to ail microscopists, afford cells of almost every imaginable shape, character, and color. Here, as with the yeast-plant, a single cell ofttimes makes up the entire organism, but, while some cells are simple, others branch and divide in all directions: some simulate the