. Botany; principles and problems. Botany. THE STEM AND ITS FUNCTIONS 91 two leaves may be exactly half way around the stem from each other, but it is much more common for their angle of divergence to be less than 180° and for the points of attachment of a series of successive leaves thus to form a loose spiral around the stem. The closeness of this spiral and the position of the leaves thereon show great diversity, but are generally constant within any par-. FiG. 42.—A tree. The shagbark hickory (Carya ovata). States Forest Service). {Courtesy United ticular species. If two leaves arise from^
. Botany; principles and problems. Botany. THE STEM AND ITS FUNCTIONS 91 two leaves may be exactly half way around the stem from each other, but it is much more common for their angle of divergence to be less than 180° and for the points of attachment of a series of successive leaves thus to form a loose spiral around the stem. The closeness of this spiral and the position of the leaves thereon show great diversity, but are generally constant within any par-. FiG. 42.—A tree. The shagbark hickory (Carya ovata). States Forest Service). {Courtesy United ticular species. If two leaves arise from^the same node they are always directly across the stem from each other and are said to be opposite in arrangement (Fig. 43). When there are more than two leaves at a node, they are disposed about the stem in a circle or whorl. Surface.—The surface of a young stem is protected only by an epidermis, but later this is replaced in wood}- plants bj^ a characteristic layer of corky cells, the bark. The necessary exchange of gases between the air and the living tissues of the. 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 Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1923
