. Elementary botany . Fig. 36. Portion of epidermis of ivy, showing irregular epidermal cells, sto and guard cells. cellular spaces are not filled with water or cell-sap, but are filled with air or some gas. Within the cells, on the other hand, we find the cell-sap and the protoplasm. 82. Stomata.—If we examine carefully the row of epidermal cells on the under surface of the leaf, we will find here and there a peculiar arrangement of cells shown at figs. 33—35. This opening through the e p i de rmal layer is a stoma. The Jr^s, l\^ KS J^(( cells which ~~\\ v^-^ ==^"<^ft \) immediately \
. Elementary botany . Fig. 36. Portion of epidermis of ivy, showing irregular epidermal cells, sto and guard cells. cellular spaces are not filled with water or cell-sap, but are filled with air or some gas. Within the cells, on the other hand, we find the cell-sap and the protoplasm. 82. Stomata.—If we examine carefully the row of epidermal cells on the under surface of the leaf, we will find here and there a peculiar arrangement of cells shown at figs. 33—35. This opening through the e p i de rmal layer is a stoma. The Jr^s, l\^ KS J^(( cells which ~~\\ v^-^ ==^"<^ft \) immediately \ ^^\ /&*J( ff surround the openings are the guard a cells. The form of the guard cells can be better seen if we tear a leaf in such a way as to strip off a short piece of the lower epidermis, and mount this in water. The guard cells are nearly crescent shaped, and the stoma is elliptical in outline. The epidermal cells are very irregular in outline in this view. We should also note that while the epidermal cells contain no chlorophyll, the guard cells do. 83. The living protoplasm retards the evaporation of water from the leaf.—If we now take into consideration a few facts which we have learned in a previous chapter, with reference to the physical properties of the living cell, we will be able to give a partial explanation of the comparative- slowness with which the water escapes iron) the leaves. The inner surfaces of the cell walls are lined with the membrane of protoplasm, and within this is the cell- sap. These cells have become turgid by the absorption of the water which has passed up to them from the roots. While the protoplasmic membrane of the cells does not readily permit the water to filter through, yet it is saturated with water, and the cla-tic cell wall with which it is in contact is also saturated. From tin- cell wall tin- water evaporates into the intercellular spaces, but the water is given up slowly through the protoplasmic mem- brane so that the wate
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisher, booksubjectbotany
