. Practical botany. Botany. STKLCTUliE V\ (JRK UK PLANTS U furniture in the room to see if you can recognize the partial rings of wood or can tell the way in which the timber was sawed. In later chapters there will be a more extensive study of stems and the ways in which they grow. 14. Leaves, general form : the epidermis. ]\Jost leaves con- sist of two parts, — the leafstalk or the petiole, and the Hade, which is the expanded portion. In some leaves the petiole is absent, and in others the blade is subdivided into several parts, m which case the leaf is said to be compound. To most obser
. Practical botany. Botany. STKLCTUliE V\ (JRK UK PLANTS U furniture in the room to see if you can recognize the partial rings of wood or can tell the way in which the timber was sawed. In later chapters there will be a more extensive study of stems and the ways in which they grow. 14. Leaves, general form : the epidermis. ]\Jost leaves con- sist of two parts, — the leafstalk or the petiole, and the Hade, which is the expanded portion. In some leaves the petiole is absent, and in others the blade is subdivided into several parts, m which case the leaf is said to be compound. To most observers leaves appear 'to be a_ uniformly green mass of mate- rial. More careful observation discloses the fact that many leaves are not equally green on both surfaces, and that running throughout the leaf there are more or less regularly arranged veins or fibrovas- cular bundles which are not green. From the upper and lower surfaces of leaves such as those of live-forever, Wan- dering Jew, Easter lily, and spiderwort one may peel a thin, almost colorless layer, which is known as the epider- mis (Fig. 10). The epidermis is composed of cells more or less compactly arranged. In the epidermis from one and sometimes from both sur- faces there are special struc- tures known as stomata (Fig. 10). From a surface view a sfowa (plural, stomata) presents two more or less crescentic or kidney-shaped cells, the guard cells, between which is an elliptical opening, the stomatal opening. Unlike other epidermal cells, the guard cells are greenish. The opening serves as a place of entrance for. Pig. 10. A surface view of leaf epider- mis from the geranium (Pelargonium) Among the ordinary epidermal cells (c) are four stomata, each with two guard cells (gc) and the mouth of an air cavity (p). Con- siderahly magnified. 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
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisher, booksubjectbotany
