Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 130 BOTANY these are several rows of rather loosely placed cells, called collectively the spongy parenchyma. These cells do not contain so much leaf green as those of the palisade layer. Notice the spaces between these cells. In some cases they can be seen to communicate with the openings of the stomata in the lower epi- dermis. Look for the cut ends of one or more of the fibrovascular bundles or veins. The cells of which they are c
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 130 BOTANY these are several rows of rather loosely placed cells, called collectively the spongy parenchyma. These cells do not contain so much leaf green as those of the palisade layer. Notice the spaces between these cells. In some cases they can be seen to communicate with the openings of the stomata in the lower epi- dermis. Look for the cut ends of one or more of the fibrovascular bundles or veins. The cells of which they are composed are seen to be greatly thickened.^ Cross Section of a Green Leaf. — The leaf in cross section shows that the whole blade is a series of tissues, the epi- dermis being somewhat thicker walled for protection, the under surface pierced by numerous pores. Each of these pores con- nects with an air space which penetrates more or less the whole inside of the leaf, but especially the layer just outside the lower epidermis. The cells of the palisade layer we shall now consider more in detail. Section of a leaf; e, epidermis; c, cells containing chlorophyll granules; p, intercellular pas- sages; g, g, guard cells of stoma. Chloroplasts. — If we examine some of the plant cells forming part of the blade of the leaf, we find cells which are almost cylindrical in form. In the protoplasm of such cells are found a number of little bodies colored green, which are known as chloroplasts or chlorophyll bodies. If we place the leaf in wood alcohol, we find that the bodies still remain, but that the color is extracted, going into the alcohol and giving to it a beautiful green color. The chloroplasts are, indeed, simply part of the protoplasm of the cell stained green. If the plant is kept in the sun, the chloro- plasts keep their green color, but in the dark this color is gradually lost. These bodies are of the greatest importance directly to plants and indirectly to animals. The chl
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