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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922. Excerpt: ... LABORATORY DIRECTIONS FOR ELEMENTARY BOTANY THE PLANT CELL All plants are composed of cells, which are sometimes called units of structure. The material to be studied first is an aquatic flowering and seed-bearing plant, whose leaves are suitable for the study of the cell. This plant is Elodea canadensis. A. Note that the Plant grows submerged in water. It is therefore aquatic. As in seed plants generally, it has stems, roots, and leaves; but is able to grow in jars in the laboratory without roots. It therefore must absorb all the materials necessary for its life from the surrounding water and through the surfaces of all its organs. Note the arrangment of leaves on the stem. Are they in whorls, that is, circles of several at the same level? Are they opposite, that is, two at the same level on opposite sides of the stem, or are they alternate, that is, in a spiral arrangement? B. The Leaf. Remove with the forceps a fresh leaf from a growing tip and mount in water. Is the leaf petiolate (having a stalk), or is it sessile, (attached directly to the stem by a broad base)? What is its size, expressed as the greatest length and width? What is its shape? Examine it with the low power of the compound microscope. What is the character of the margin? Notice a dark line through the middle of the leaf from the base to the apex. This is the mid-rib-The broad expanded portion is the blade, or lamina. Dark lines running parallel to the mid-rib are not secondary ribs, but intercellular spaces, filled with some gas, which in bright sunlight is likely to be pure oxygen. Why? Looking at the finer structure of the leaf, note the boundaries of individual cells, showing as very thin white lines. Examine all parts of the leaf and note differences in size, shape, and color of ce...
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