File:Botany of the living plant (1947) (20218670100).jpg

Title: Botany of the living plant
Identifier: botanyoflivingpl00bowe (find matches)
Year: 1947 (1940s)
Authors: Bower, F. O. (Frederick Orpen), 1855-1948; Wardlaw, C. W. (Claude Wilson), 1901-
Subjects: Botany; Plants
Publisher: London, Macmillan and Co. , ltd.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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BOTANY OF THE LIVING PLANT While the main axis of the "Christmas Tree" is upright and ,,1 the lat.-r,! branches appear flattened. This is due partly to the fact that the lateral branches of higher order have been developed from buds seated right and left on the main branches ; partly to the curvature of the leaves upwards. Nevertheless the construction of these dorsiventral branches is essentially radial. If the terminal bud of the main stem be removed, one or more of the lateral buds, which would normally grow into flattened lateral branches, will grow up- wards and take its place. With the vertica-1 position, it regains its radial symmetry. Very much the same may be seen in the Sycamore, or the Horse Chestnut, both of which retain the radial structure of the leading shoot. Their lateral branches are slightly dorsiven-
Text Appearing After Image:
Fig. 138. Strongly dorsiventral branch of Lime, seen from above. Its leaves form a compact leaf-mosaic. (Reduced to J.) tral, but they do not modify the symmetry of the lateral branches so much as the Spruce. On the other hand, the upright radial shoot, or leader, in many trees may itself become dorsiventral as growth proceeds, while the lateral \ "ranches are conspicuously so. Consequently the whole tree when full grown will be made up of flattened shoots, the lateral branches spreading out like fans. (Fig. 138.) In the Elm, Beech, and Lime this change of the leading shoot comes early. Their seedlings are radially constructed. In the Elm and Beech the dorsiventral structure, with alternate distichous leaves (in place of the decussate arrangement) app n the second year of the seedling, and continues from then onwards. Bui though the whole tree is thus built up of dorsiventral shoots, these may form collectively a radial crown, as in the Elm. Such examples of the transition from radial to dorsiventral symmetry are carried out in each individual plant. They indicate that the radial is the more primitive state, and the dorsiventral derivative.

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