Elementary botany . arge num-bers of plants of the same speciesare growing close together, theycan maintain practically thesame habit as where growingalone; (3) the advantage gainedby other types in their neighbor-hood in less shading than if thetype were spreading. The cyl-indrical type can, therefore, growbetween other types with lesscompetition for existence. 716. The cone type.—This iswell exampled in the larches,spruces, the gingko tree, someof the pines, cedars, and othergymnosperms. In the cone type,the main axis extends throughthe system of branches like atall shaft, , the trunk is
Elementary botany . arge num-bers of plants of the same speciesare growing close together, theycan maintain practically thesame habit as where growingalone; (3) the advantage gainedby other types in their neighbor-hood in less shading than if thetype were spreading. The cyl-indrical type can, therefore, growbetween other types with lesscompetition for existence. 716. The cone type.—This iswell exampled in the larches,spruces, the gingko tree, someof the pines, cedars, and othergymnosperms. In the cone type,the main axis extends throughthe system of branches like atall shaft, , the trunk is excur-rent. The lower branches arewide-spreading, and the branchesbecome successively shorter,usually uniformly, as one ascendsthe stem. The branching is of two types: (1) the branches are in false whorls; (2) the branches ^KPisl^^H K B B 0 L H B Jp?-K*f$%:!*?qjft ^m wVv ^w *« i v/j^^5^ Wk s : Br ?? -* *v^;~^aP |^L m ^Br^mm\ K JHI i^k | ^7^!11 Rfffw w Fig. stem of mullein. TYPES OF STEMS. 367. are distributed along the stem. To the first type belong thepines, Norway spruce, Douglas pruce, etc. The white pine isan exquisite example, and inyoung and middle-aged treesshows the style of branching tovery good advantage. Thebranches are nearly horizontal,with a slight sigmoid gracefulcurve, while towards the top thebranches are ascending. Thisdirection of the branches is dueto the light relation. The fewwhorls at the top are ascendingbecause of the strong light fromabove. They soon become ex-tended in a horizontal directionas the main source of light isshifting to the side by the shad-ing of the top. The ascendingdirection first taken by the upperbranches and their subsequent turning downward, while the endsoften still have a slight ascending direction gives to the olderbranches their sigmoid curve. The young vernal shoots of the pines show some very interest-ing growth-movements. There are two growth periods: (1) theelongation of the shoot, and (2) the elongation
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Keywords: ., bookauthoratk, bookcentury1900, bookdecade1900, booksubjectbotany
