. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. ROOTS AS TO ORIGIN 125 upper parts of these plants die. You know that roots of some plants can directly produce new plants. All these facts are important, but they form no more than a starting point in the study of roots. 42. Roots as to Origin. — Roots come from the em- bryo, or from other roots, or from the shoot. Those which come from the embryo or branch off from other roots are called primary; those which arise from the shoot are called secondary. Lea
. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. ROOTS AS TO ORIGIN 125 upper parts of these plants die. You know that roots of some plants can directly produce new plants. All these facts are important, but they form no more than a starting point in the study of roots. 42. Roots as to Origin. — Roots come from the em- bryo, or from other roots, or from the shoot. Those which come from the embryo or branch off from other roots are called primary; those which arise from the shoot are called secondary. Leaves as weU as stems sometimes give off roots as branches. The leaf of begonia is an ex- ample. This plant may be propagated by means of cuttings from the leaves. A. Primary Roots. — You remember that the embryo comes from a single cell which is produced by the union of two other cells. (See page 58.) This new cell by repeated divisions and by growth forms the embryo. Certain cells of the embryo develop into the original primary root. (See Figure j8.) Sometimes this original primary root grows straight down and becomes much larger than any of its branches. Such a root is called a tap-root. Dandelions, radishes, turnips, carrots, and parsnips have tap-roots. (See Figure jp.) Tap-roots are more commonly used for storage than are other forms of roots. More often, however, a tap-root is not formed. The primary root divides into many branches of about equal size. Such roots are called fibrous. Corn has fibrous Fig. 38. — Seedling of com showing the de- velopment of primary 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 G. (John Gaylord), b. 1876. New York, American Book Co
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