Abstract
Cohen, L. I. (Washington State U., Pullman.) Studies on the ontogeny of the dwarf mistletoes, Arceuthobium. I, Embryogeny and histogenesis. Amer. Jour. Bot. 50(4): 400–407. Illus. 1963.—A complete developmental study on the origin and organization of the main tissue systems in the embryo of Arceuthobium reveals a greater degree of internal differentiation in the mature embryo than hitherto reported. The mature embryo consists of rudimentary cotyledons, a well‐defined hypocotyl and a highly organized radicle. The latter develops from the remaining undifferentiated portion of the globular embryo soon after the embryonic cortex and procambium are differentiated. The radicular promeristem is organized into 4 initiating zones: (1) a uniseriate layer of apical surface initials; (2) a subapical zone of central initials; (3) a peripheral zone; and (4) a zone of procambium initials. Comparison between the dwarf mistletoe embryo and those of several nonparasitic angiosperms indicates that their ontogenies, in many respects, are essentially similar.