File:The ecological relations of roots (1919) (14586808909).jpg

Identifier: ecologicalrelati00weav (find matches)
Title: The ecological relations of roots
Year: 1919 (1910s)
Authors: Weaver, John E. (John Ernest), 1884-1966
Subjects: Roots (Botany) Plant ecology
Publisher: Washington, Carnegie institution of Washington
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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Fig. 28.—Gilia longijlora. system of fine absorbing rootlets, branched to the second and third order,is found. Below the point where the tap throws off the larger laterals, it ismuch more poorly branched, the branches being relatively much smaller andshorter, but well supphed with fine rootlets, as are the laterals above. Fromthe figure and description it will be seen that although this is an annual, theabsorptive system is characteristic of that of most of the species found in thesandhills. The roots are glistening white and quite tough for herbaceous plants. Euphorbia petaloidea.—Euphorbia is a sandhill pioneer which forms bothfamilies and colonies. The root system begins with a strong, smooth tap-root, varying in diameter according to the age and size of the plant, the
Text Appearing After Image:
78 THE ECOLOGICAL RELATIONS OF ROOTS. largest examined being 4 mm. in diameter. This tap penetrates almostvertically downward. Beginning at a depth of 2 to 3 inches, it sends offmultitudes of fine fibrous roots which are much branched and penetrate thesoil on all sides to a distance from a centimeter or less to 3 or 4 inches. Inaddition to these finer roots, the tap sends off longer laterals which traversethe soil in all directions, some taking a course almost parallel with the sur-face, while others pass off more obliquely. These vary in length, some being10 to 12 inches long. The laterals are much branched and rebranched, andtogether with the finer rootlets form an effective absorbing system. Usuallyat a depth of 5 to 8 inches the tap divides up into such a system of largelaterals as to almost if not quite lose its identity. These lower laterals varyfrom 0.5 to 1 mm. in diameter and diverge more or less obliquely downward,some penetrating to a depth of 26 inches or more. The deeper

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