. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 50 THE ROOT, OR DBSCENDING AXIS. etc., the common difference being also five); two sets (one of tliree, the other of eight) turning left; and stih another set, of thirteen, steepest of all, turning right (1â14â27, etc.). Now the sum cf the spirals contained in the two steepest sets gives the denomincUor of the fraction expressing the true formative spiral sought. Thus, 8-|-13=21. The numerator corresponding is already known,
. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 50 THE ROOT, OR DBSCENDING AXIS. etc., the common difference being also five); two sets (one of tliree, the other of eight) turning left; and stih another set, of thirteen, steepest of all, turning right (1â14â27, etc.). Now the sum cf the spirals contained in the two steepest sets gives the denomincUor of the fraction expressing the true formative spiral sought. Thus, 8-|-13=21. The numerator corresponding is already known, and the fraction is Jj. See also the white pine cone, whose cycle is J^. 238. Diagram 97 represents the leaves of a cherry oyde as seen from ahove, and verified in the aestivation of the fiowers in the rose-family. V MORPHOLOGY OF THE LEAF. 239. General character. The leaf may be regarded as an expan- sion of the substance of the bark, extended into a broad thin plate by means of a woody frame work or skeleton, issuing from the inner part of the stem. The expanded portion is called the lamina or blade of the leaf, and it is either sessikj that is, attached to the stem by its base, or it is petiolate, attached to the stem by a footstalk called the petiole. 240. Stipules. But the regular petiole very often bears at its base a pair of leaf-like appendages, more or less ap- parent, called stipules. Leaves so appendaged are said to be stipulate, otherwise they are ex- stipulate. 241. Therefore a complete leaf consists of three distinct parts; the lamina or blade, the petiole, and the stipules. 242. Transformations. Both the petiole, blade and stipules are subject to numerous mod- ifications of form. Either of them may exist without the others, or they may all be transformed into other organs, as pitchers, spines, tendrils, I and even into the organs of the flower, as will /' hereafter appear. OF THE PETIOLE. 243. The form of the distinct petiole is rarely cylindrical, but more gen
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