. Botany for academies and colleges: consisting of plant development and structure from seaweed to clematis. Botany; 1889. 160 ACADEMIC BOTANY. 393. Leaf-epidermis.—The. cells of the leaf-epidermis (Fig. 233) are flattened, coherent by their edges, and variously shaped. Here and there between the walls of two adja- cent cells small open- ings appear (Fig. 233, s, s); these are the storaata. The stomata communioate with the air-chambers and lacunes [1) in the paren- chyma, thus making direct connection between the plant and the open air and establishing thorough cir- culation from the topmost l
. Botany for academies and colleges: consisting of plant development and structure from seaweed to clematis. Botany; 1889. 160 ACADEMIC BOTANY. 393. Leaf-epidermis.—The. cells of the leaf-epidermis (Fig. 233) are flattened, coherent by their edges, and variously shaped. Here and there between the walls of two adja- cent cells small open- ings appear (Fig. 233, s, s); these are the storaata. The stomata communioate with the air-chambers and lacunes [1) in the paren- chyma, thus making direct connection between the plant and the open air and establishing thorough cir- culation from the topmost leaf of the tallest tree to the fibrils of its deepest root. We have already There are no stomata in Fig. 233.—Epidermi" of If. of Jf)ower-de luce (TrU gprnumica); s, s, stomata', p,p, cuticle, or pellicle; /, opening in the cuticle, corresponding to the stomata of the epidermis, which has been removed. seen them in the Acrogens (Fig. 29). Thallogens. 394. The plant respires through the stomata as animals do through the pores of the skin, exhaling certain elements and inhaling others. Each stoma consists of two oblong cells, which have been compared to lips; they open or shut the orifice, thus controlling respiration. These tiny door-keepers do their work with exemplary fidelity ; open- ing wide when the air is moist, that inhalation may. be promoted, but closing promptly when it is dry, lest the precious juices should be con- sumed by drought. The stomata, like the air-chambers, are most abundant on the under surface of the leaf. The vine has none on its upper face, and 13,000 to the square inch on its lower one. The lilac has few on its upper face, and 160,000 to the square inch on the lower. The mistletoe has nearly an equal number on each face,—200 to the square inch. 395. The Outicle, or Pellicle (L. pellicula, little skin), is a thin membrane covering the epidermis (Fig. 233, p, p). It has no cells, but is a mere expansion of the cell-wall, and separable from it
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