Elementary botany . Fig. 51. Stoma open. Figs. 34, 35.—Section through stomata of ivy leaf. 42 PHYSIOLOG Y. cellular spaces are not filled with water or cell-sap, but are filledwith air or some gas. Within the cells, on the other hand, wefind the cell-sap and the protoplasm. 82. Stomata.—If we examine carefully the row of epidermalcells on the under surface of the leaf, we find here and therea peculiar arrangement of cells shown at figs. 51, 52. This openingthrough theepi dermallayer is astoma. Thecells whichi m mediatelysurround the. Fig. of epidermis of ivy, showing irregular epid
Elementary botany . Fig. 51. Stoma open. Figs. 34, 35.—Section through stomata of ivy leaf. 42 PHYSIOLOG Y. cellular spaces are not filled with water or cell-sap, but are filledwith air or some gas. Within the cells, on the other hand, wefind the cell-sap and the protoplasm. 82. Stomata.—If we examine carefully the row of epidermalcells on the under surface of the leaf, we find here and therea peculiar arrangement of cells shown at figs. 51, 52. This openingthrough theepi dermallayer is astoma. Thecells whichi m mediatelysurround the. Fig. of epidermis of ivy, showing irregular epidermaand guard cells. cells openings are the guard stoma cells. T h e form of the guard cells can be better seen if we tear a leaf in such a way asto strip off a short piece of the lower epidermis, and mount thisin water. The guard cells are nearly crescent shaped, and thestoma is elliptical in outline. The epidermal cells are veryirregular in outline in this view. We should also note that whilethe epidermal cells contain no chlorophyll, the guard cells do. 82a. In the ivy leaf the guard cells are quite plain, but in mostplants the form as seen in cross-section is irregular in outline, asshown in fig. 530, which is from a section of a wintergreen leaf is interesting because it shows the characteristic struc-ture of leaves of many plants growing in soil where absorption ofwater by the roots is difficult owing to the cold water, acids, orsalts in the water or soil, or in dry soil (see Chapters 47, 54? 55)*The cuticle ov
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