Identifier: ecologicalrelati00weav 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 View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: ally run off in a horizontal direction, sometimes for nearly 3 feet beforeturning downward. The end of the tap-root is either unbranched or branchedbut little, and is often dead. Hard soil seems to be a marked hmiting factorto root growth, and under this condition, especially, the usual very irregularcourse of descent is greatly emphasized. Twenty-four root systems wereexamined. While one plant penetrated to 9.5 feet, the average depth wasfound to be 5.5 feet (fig. 6). Wyethia amplexicaulis.—This large, rather coarse plant is at home onmoist hiUsides and especially in valleys, where it forms extensive estivalsocieties. It has a fleshy tap-root, which sometimes measures 9 inches incircumference and may reach a depth of 6 feet 5 inches. It usually has severalstrong laterals which come off from 8 inches to 3 feet in depth, and may runout in a somewhat horizontal direction for 3 or 4 feet from the main root.Often at a depth of 1 to 3 feet the whole tap breaks up into 2 to 5 nearly equal Text Appearing After Image: THE PRAIRIES OF THE PACIFIC NORTHWEST. 37 parts which pursue a downward course, or later extend out as laterals. Pri-mary laterals are not much branched. The w^hole root from crown to near thetip is covered with scattered small laterals, usually not over 2 mm. in diameter.These are poorly branched, not often giving off roots of the fourth order. Thetip of the main root hkewise is Httle branched. The roots dry out and shrinkrapidly upon removal from the soil. The 18 plants examined had an averageroot depth of 5 feet (fig. 7). Heuchera glabella.—This saxifrage has a strong tap-root supplied, especiallyin the first foot of soil, with rather numerous but poorly branched laterals.It reaches depths of about 5 feet (fig. 8). Leptotsenia miiltifida.—Leptotcenia is a subdominant which forms con-spicuous societies in the vernal aspect. It has a large fleshy tap-root, some-times 7 inches in circumference, wiiich may reach a depth of over 5 feet. Thefusiform roots may narrow down gradually or Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.