Coleoptile of Zea mays and Other Grasses

Abstract

Whether the coleoptile in grasses is to be interpreted as a single leaf, or as the result of the union of two organs, is still a matter for discussion. SARGANT and ARBER' favor the theory that the coleoptile is the equivalent of a pair of fused stipules. WORSDELL2 substantially agrees, concluding that it is a ligular-like structure formed by the union of stipules. They base their interpretations principally on the presence of the two vascular bundles characteristically present in the coleoptiles of most grasses. These two bundles establish a symmetry in the coleoptile. Recently, however, PERCIVAL3 has shown that in the coleoptiles of an Indo-Abyssinian emmer wheat (Triticum dicoccum Schtibl.) from two to six bundles may be present. He has construed the presence of these several bundles as evidence in favor of the coleoptile being a single leaf, and not in origin. Further evidence in favor of the single leaf theory, as set forth by PERCIVAL in Triticum dicoccum, is supplied by the writer's observations on some I 5,000 seedlings of Zea mays L. The greater number of plants examined represented different strains of the varieties Golden Glow, Ninety-Day Yellow Dent, and Golden Bantam. In addition Dwarf, Liguleless, and Chinese Suckering strains were observed. Certain strains of the Golden Glow variety showed more than two bundles in the coleoptile. Two to five bundles were observed to be present (figs. I-4). These additional bundles destroy the double symmetry of the coleoptile. The position of the bud in the axil of the coleoptile should also be of some significance in determining whether it is a single structure,