File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14596842518).jpg

Identifier: naturalhistoryof01kern (find matches)
Title: The natural history of plants, their forms, growth, reproduction, and distribution;
Year: 1902 (1900s)
Authors: Kerner von Marilaun, Anton, 1831-1898 Oliver, Francis Wall, 1864- Macdonald, Mary Frances Ewart Busk, Marian Balfour, Lady
Subjects: Botany
Publisher: London, Blackie
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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vious year, whatmay be termed a new richly-leaved and thickly overshadowing little maple-treegrows up. That mutual consideration, which is otherwise observed by membersof the same plant, and which was described earlier, here ceases. The leaves ofthe topmost shoot are, of course, so arranged that no mutual injury is done;but very little attention appears to be paid to the leaves below, as little perhapsas to the lower grasses and herbs which grow under the maple-tree on theground. But what are the branches to do which spring from the buds in the centreof the maple-tree under consideration? If they take the same direction as thebranches at the extreme summit, they will come into the area of the dark shadowsthrown by the numerous broad leaves of the top branches. They are, therefore,compelled to take up another direction if their leaves are not to perish fromwant of light. And, as a matter of fact, this is what they do. They arrange RELATION BETWEEN POSITION AND FORM OF GREEN LEAVES, 415
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416 RELATION BETWEEN POSITION AND FORM OF GREEN LEAVES. themselves, that is to say, more or less horizontally, and increase in length inthis direction until their leaves project outside the shadow of the topmost leafybranches, so that they may be able there to catch the sunlight. All this isobserved not only in maples, which have been selected as examples, but in allrichly-leaved trees and shrubs; the topmost branches are directed verticallyupwards, the next lower rise obliquely, those still lower extend horizontally,and the lowest of all frequently even incline earthwards. The twigs of the older, lower brancheswhich have grownout beyond theshaded area oftenagain try to rise,and assume a direc-tion which is almostsimilar to that ofthe highest branchesat the summit. Suchbranches and twigsthen display a cur-vature which is likea Roman f\J lyingsideways. Oaks andhorse-chestnut treesfurnish strikingexamples of this.The phenomenon isshown still betterin firs (see fig. 105),in which the twi

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