On the origin of cotyledon and epicotyl inPotamogeton indicus

Summary The appearance of the first vertical wall in the terminal hemispherical cell of the proembryo ofPotamogeton indicus is indicative of the origin of the cotyledonary and epicotylary loci. The cotyledonary locus grows at a faster rate while the epicotylary region conspicuously lags behind. Topographically the cotyledonary and epicotylary loci are adjacent to each other, both being derived from the terminal tier of the proembryo. The subjacent tiers, including them tier, do not take part in the organization of the shoot apex but only contribute to the formation of the hypocotyl and root regions.