Floating Stomates (Adetostomy) in Ferns: Distribution and Ontogeny

A unique guard cell apparatus occurs in certain species of Anemia (Schizaeaceae) and in certain species of the unrelated family Polypodiaceae. A guard cell pair is completely surrounded by one epidermal cell, with no attachment to lateral (anticlinal) walls of adjacent epidermal cells. This condition of “floating stomates” is called adetostomy. In rare cases the surrounding epidermal cell is in turn entirely enclosed by another single epidermal cell. The ontogeny of floating stomates has been variously interpreted. This study supports the early view of Rauter that a funnel‐shaped guard mother cell is initiated in place entirely within a protodermal cell.