Title: Botany of the living plant
Identifier: cu31924001307853 (find matches)
Year: 1919 (1910s)
Authors: Bower, F. O. (Frederick Orpen), 1855-1948
Subjects: Botany
Publisher: London, Macmillan and co. , limited
Contributing Library: Cornell University Library
Digitizing Sponsor: MSN

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MODIFICATIONS OF FORM 169 leaves of each succeeding whorl alternate as a rule with those of the preceding, so that they occupy the spaces between them, an arrange- ment that is very convenient in the packing of the crowded parts into small compass in the bud. A transition to higher numbers in the cycle may be seen in the individual plant. Thus in Fuchsia, which has usually decussate leaves, a very strong shoot may bear alternating whorls of three. In Lysiiiiachia vulgaris, and in the Privet, a like variability is common. It is styled meristic variation, and one factor in producing it is probably the size of the apical cone, \\'hich, when
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Fig. iiy. Young leafy shoot of sycamore seen from aho\-e ; showing how with ver\- tittle o\'erlappiiig the leaf-blades form a mosaic. The spaces tnioccupied centrally A\ill he tilled as the y^oiinger lea\'es c-xpand. large proportionally to the leaf-primordia, can accommodate a larger number of young leaves at the same level. Such variations are common in the floral region, where cyclic arrangements prevail. (Compare Floral Diagrams in Appendix A.) But in most Dicotyledons, and very generally in Monocoty- ledons, the arrangement of the leaves is alternate ; that is, they are seated singly, each at a dift'erent level upon the axis. The arrange- ment is often such that an ascending spiral line may be drawn round the stem so as to thread together the bases of them all. Such arrange- ments are therefore described as spiral. That the cyclic and spiral modes of arrangement arc not essentially distinct from one another is shown by the fact that both may appear successively in the same plant. For instance, in the Sunflower, the seedling starts with paired

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