. Plant life, considered with special references to form and function. Plant physiology. THE S TEM. 97. therefore, crowded. They may be so crowded as to completely envelop the stem and hide it from view. This is well seen in the scale-like leaves of such plants as the pines (fig. loi), cedars, and arbor vitae (fig. log). Or, certain of the internodes may elongate, while others remain undeveloped. For example, in the shepherd's- purse, the first internodes remain short, so that the lower lea\-es are crowded into a tut"t ^ic. 109.âa shoot of arbor \it3; or white cedar, snouing scale lea\es
. Plant life, considered with special references to form and function. Plant physiology. THE S TEM. 97. therefore, crowded. They may be so crowded as to completely envelop the stem and hide it from view. This is well seen in the scale-like leaves of such plants as the pines (fig. loi), cedars, and arbor vitae (fig. log). Or, certain of the internodes may elongate, while others remain undeveloped. For example, in the shepherd's- purse, the first internodes remain short, so that the lower lea\-es are crowded into a tut"t ^ic. 109.âa shoot of arbor \it3; or white cedar, snouing scale lea\es covering or rosette; the following inter- ^t^â¢- >-'alural size.âAfter Kemer. nodes are elongated, the corresponding leaves being scattered at regular intervals : while, still higher, the internodes are again shortened and the leaves brought into close clusters in the flowers. 120. The consistence of the stem depends upon the relative amount of mechanical tissues which it contains. Stems may be designated as woody, solid, or fleshy, terms which need no further definition. 121. The shape of the stem varies in difterent plants. Verv commonly the stem as a whole is looked upon as cylindrical, but, if carefully considered, it will be seen that the diameters of successive internodes at first become gradually greater, and, after maintaining this maximum for a time, grow gradually less. The stem is, therefore, a cylinder with more or less conical ends. If the attainment of the maximum diameter is sudden, and the diminution similarly sudden, the resulting stem will ha^â e the shape of a double cone. The modification of such a form into the spherical is not difiicult to imagine. Striking illustrations of these extreme forms are to be found among the cactuses (hg. no).. 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 t
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