. Essentials of botany. Botany; Botany. MINUTE STRUCTURE OF LEAVES 129 the square inch, or the black walnut, with nearly 300,000 to the square inch, the total number on a tree is incon- ceivably large. 152. Uses of the Parts examined. — It will be most con- venient to discuss the uses of the parts of the leaf a little later, but it will make matters sim- pler to state at once that the epidermis serves as a mechan- ical protection to the parts beneath and prevents exces- sive evaporation, that the palisade- cells (which may not be made out very clearly in a roughly prepared section) hold large
. Essentials of botany. Botany; Botany. MINUTE STRUCTURE OF LEAVES 129 the square inch, or the black walnut, with nearly 300,000 to the square inch, the total number on a tree is incon- ceivably large. 152. Uses of the Parts examined. — It will be most con- venient to discuss the uses of the parts of the leaf a little later, but it will make matters sim- pler to state at once that the epidermis serves as a mechan- ical protection to the parts beneath and prevents exces- sive evaporation, that the palisade- cells (which may not be made out very clearly in a roughly prepared section) hold large quantities of the green coloring mat- ter of the leaf in a position where it can receive enough but not too much sunlight, and that the cells of the spongy parenchyma share the work of the palisade-cells, besides evaporating much water. The stomata admit air to the interior of the leaf (where the air spaces serve to store and to distribute it), they allow oxygen and carbonic. Fig. 94. A Stoma of Thyme, magnified.) (Greatly A, section at right angles to surface of leaf; B, surface view of stoma. c«, cuticle; g, guard- cells ; s, stoma; e, epidermal cells; a, air chamber; c, cells of spongy parenchyma with grains of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1908
