THE PROBLEM of homologies in the embryos of the Gramineae has long interested students of morphology and anatomy. Extensive developmental studies of embryos and seedlings of members of this group have been carried on for almost a century and a half, and the first description of grass embryos was published more than a century earlier by Malpighi in 1687. It would seem, therefore, that homologies would have been well worked out, but that this is not the case is evidenced by the conflicting views held by various authors continuing to the present time. Bennett (1944) states: homologies of these organs [scutellum, epiblast, and coleoptile] are still a controversial subject, and Artschwager and McGuire (1949) go so far as to say: Homologies in grass embryos and seedlings today remain one of the most controversial subjects in botany. They conclude their paper with the following statement: . objective interpretation of the nature of scutellum, coleoptile, and axis interval between first node and coleoptile offers approximately the same difficulties as when workers on embryo and seedling structure in grasses first attempted it more than a century ago. Since extensive reviews of the literature are to be found in papers by Van Tieghem (1872), Bruns (1892), Kennedy (1899), Avery (1930), and McCall (1934), it seems unnecessary to present here more than a summary of the conflicting views. The present study contributes only to the interpretation of the homology of the coleoptile, hence discussion will be largely confined to that organ. A review of the literature on this subject reveals that the coleoptile has been interpreted in the following ways: (1) The coleoptile is the first leaf of the plumule, or the second leaf of the plant, the scutellum being the cotyledon. Some authors have considered the epiblast to be a rudimentary cotyledon, and in this case the coleoptile would be the third, rather than the second, leaf of the plant. It would still be, however, the first leaf of the plumule. (2) The scutellum and the coleoptile together form the cotyledon. The coleoptile is variously interpreted as a ligule, as a pair of fused stipules, or as an extension of the cotyledonary sheath. (3) The coleoptile is the cotyledon and the scutellum is an outgrowth of the radicle or of the axis. (4) The coleoptile and scutellum are structures