. The botany of crop plants : a text and reference book. Botany, Economic. 72 BOTANY OF CROP PLANTS leaf which is wrapped about the stem) of the first few leaves, or spring freely from underground stems. They may also arise from joints above the ground hne, as in corn. If such aerial roots reach the ground they may serve as supporting or "prop" roots (Fig. 56). Stems.—General Characteristics.—The stems of grasses are called culms. They are cylindrical (rarely flattened), and divided into sections Stem- jheatb drowinO zones °& internode^ node. (internodes) (Fig. 25) which are usua
. The botany of crop plants : a text and reference book. Botany, Economic. 72 BOTANY OF CROP PLANTS leaf which is wrapped about the stem) of the first few leaves, or spring freely from underground stems. They may also arise from joints above the ground hne, as in corn. If such aerial roots reach the ground they may serve as supporting or "prop" roots (Fig. 56). Stems.—General Characteristics.—The stems of grasses are called culms. They are cylindrical (rarely flattened), and divided into sections Stem- jheatb drowinO zones °& internode^ node. (internodes) (Fig. 25) which are usually hollow, but some- times filled with pith, as in corn. When young, the in- ternodes are solid, but, as the stem enlarges, the central portion is ruptured and a hollow is formed. The nodes (Fig. 25), the enlarged joints between the internodes, are soHd. Enlargement of the nodes is due partly to a thickening of the leaf base at each node (Fig. 26) and partly to enlargement of the stem itself. In most grasses, the part of the culm within the sheath remains soft and continues to grow or retain the power of growth after the portion not in the sheath has ceased growth, or lost the ability to grow. The youngest part of each internode is at its base, surrounded by the basal swelling of the leaf sheath (Fig. 26). Each internode has its own growing zone. Lodging.—It is customary to speak of a grass as "lodged" Fig. 26.—Barley. A, portion of leaf at juncture of leaf and blade; B, stem cut in median lengthwise section. x 2} 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 Robbins, Wilfred William, 1884-1952. Philadelphia : P. Blakiston's Son
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