Identifier: plantstheirway00ston (find matches)
Title: Plants and their ways in South Africa
Year: 1915 (1910s)
Authors: Stoneman, Bertha, 1866-
Subjects: Plants
Publisher: London, Longmans, Green
Contributing Library: The LuEsther T Mertz Library, the New York Botanical Garden
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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Fig. 56.—Orchid stem with leaves arranged on opposite sides of the stem. The leaves of the Orchid in Fig. 56 have broad baseswhich encircle the stem. They are arranged in two rows, sothat, calling the lowermost leaf No. i, the third and fifth willbe directly over it. The distance from one midrib to anotheris one-half the distance around the stem. Canna and Kei Apple have broad thin leaves, the fourth isover the first, so that the second and third are exposed to the 4 50 Plants and their Ways in South Africa light. The distance from the midrib of one leaf to that ofanother is one-third the distance around the stem. What leafwill come over the fourth ? This may be found by drawing a
Text Appearing After Image:
Fig. 57.—Spirals showing J, §, § Phyllotaxy. spiral and dividing it into three sections. Imagine the centreto be the tip of the stem. Beginning where one of the linescuts the outer end of the spiral, place leaf number one. Twoand three will fall on the other lines. The fourth will be inline with the first. By placing each succeeding leaf one-third A Study of Leaves 51 of the way around the spiral, the seventh will fall on the linewith the first and fourth. Aloe ciliaris bears the sixth leaf over the first. Thedistance from leaf to leaf is two-fifths of the way around thespiral. What leaf will come over number three ? Thedistance from one leaf to the one next younger is called theangle of divergence. Other Aloes have different angles of di-vergence. Besides the ^, \^ ; divergence, the fractions ;, y%, ^ywill represent the arrangement on Proteas and other plants withleaves attached by narrow bases. Still other arrangements maybe found. Besides the spiral arrangement, leaves are freq

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