A Summary of Chromosome Numbers in the Marsileaceae, with Counts for Additional Species of Marsilea

Abstract

Marsileaceae is a family of aquatic ferns containing three closely related genera: Marsilea, Pilularia, and Regnellidium. The genus Marsilea contains perhaps 50 species worldwide, while Pilularia contains six, and Regnellidium only one (Tryon & Tryon, 1982). All three genera have creeping, branched, and matted rhizomes bearing roots and upright leaves. They can be found growing rooted in aquatic environments or on land. The leaves of Pilularia are devoid of lamina, while those of Regnellidium bear two opposite pinnae, and those of Marsilea bear two pairs of pinnae (Bierhorst, 1971).