. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 104 PHYLLOTAXIS OE LEAF-AEEANGEMENT. of turns, and the denominator the number of leaves in the spiral cycle. Thus, in fig. 214, ab, the cycle consists of five leaves, the 6th leaf being placed vertically over the 1st, the 7th over the 2d, and so on; while the number of turns between the 1st and 6th leaf is two : hence, this arrange- ment is indicated by the fraction |. In other words, the distance or divergence between the first and second leaf, ex- pressed in parts of
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 104 PHYLLOTAXIS OE LEAF-AEEANGEMENT. of turns, and the denominator the number of leaves in the spiral cycle. Thus, in fig. 214, ab, the cycle consists of five leaves, the 6th leaf being placed vertically over the 1st, the 7th over the 2d, and so on; while the number of turns between the 1st and 6th leaf is two : hence, this arrange- ment is indicated by the fraction |. In other words, the distance or divergence between the first and second leaf, ex- pressed in parts of a circle, is | of a circle, or 360° -M = 144°. In fig. 211, a b, the spiral is ^, one turn and two leaves ; the third leaf being placed verti- cally over the first, and the divergence between the first and second leaf being one-half the circumference of a circle, 360° -H J = 180°. Again, in fig. 215, a b, the number is i, or one turn and three leaves, the angular divergence being 120°. The general forms of Phyllotaxy may be brought out by a con- tinued fractionâ 1. Fig. 215. a+l + l + l + 1, etc., where a may have the values 1, 2, 3, or 4, etc. The actual fractions thus resulting areâwhen « = 1-* -I f * A, etc. » = 2,..i i i 1 A> etc. a = 3. 1 â¢s 1 T â f A A etc a = 4. â i i f A- A> etc Each fraction being obtained by adding together the numerator and denominator in the two preceding fractions. When the leaves or scales are alternate, and run in a single series, they are unijugate ; when the leaves are opposite, and there are two parallel rows produced, the arrangement is bijugate, while in the case of whorled leaves the arrangement may be trijugate or quadrijugate. Fig. 215.â^Young plant of Cyperus esculentus, wil^ii leaves in three rows, or tristichous, expressed by the fraction i, or one turn and three leaves, a, The plant, with its leaves numbered in their order. â i. Magnified representation of the stem, showing the insertion of th
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
