. Plants; a text-book of botany. Botany. 94 PLANT RELATIONS. "layering,'-' by which a stem, as a bramble, is bent down and covered with soil. The covered Joints strike root, and the pulling follows (see Fig. 86). A very plain illustration of the same fact can be obtained from many crevice plants. These plants send their root systems into the crevices of rocks, and spread a rosette of leaves against the rock face. In the next year a new rosette of leaves, developed further. Fig. 89. Section through the leaf of a quillvvort {Isoefes), showing the four large air chambers («), the central vas
. Plants; a text-book of botany. Botany. 94 PLANT RELATIONS. "layering,'-' by which a stem, as a bramble, is bent down and covered with soil. The covered Joints strike root, and the pulling follows (see Fig. 86). A very plain illustration of the same fact can be obtained from many crevice plants. These plants send their root systems into the crevices of rocks, and spread a rosette of leaves against the rock face. In the next year a new rosette of leaves, developed further. Fig. 89. Section through the leaf of a quillvvort {Isoefes), showing the four large air chambers («), the central vascular region {&), and the very poorly developed cortex. up the stem, is also found against the rock face. It is evident that the stem has been pulled back into the crevice enough to l)ring the new leaves against the rock, and this pulling has been effected by the new roots, which have laid hold of the crevice soil, or walls. (:)) Soil dangerx.—In this connection certain soil dan- gers and the response of the roots should be noted. The soil may become poor in water or poor in certain essential materials, and this results in an extension of the root sys-. 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 Coulter, John Merle, 1851-1928. New York, D. Appleton and company
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