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Family: Marsileaceae

Kingdom: Plantae Rank: Family Parent: Hydropteridales Status: Valid

Common Names:

  • WATER-CLOVER FAMILY - English, United States of America
  • PEPPERWORT FAMILY - English, United States of America

Morphological Description

Family Recognition in the Field: Plants of wet areas with leaves resembling a 4-leaf clover (in 1 species apparently rare in East TX the leaves thread-like and _ resembling those of a grass); sori in hard, bean- or pea-like structures near the base of the petioles.

Diagnosis: Plants aquatic or of very wet habitats; stems (rhizomes) long-creeping; leaves scattered along the stems, long-petioled and palmately divided into 4 pinnae or else filiform and lacking expanded blades; sori contained in sporocarps (= hard bean- or pea-like structures which are apparently highly modified pinnae) on stalks from near base of petiole; sporangia of 2 kinds within the same sorus, the megasporangia with 1 megaspore, the microsporangia with numerous microspores.

Other

Notes: A nearly cosmopolitan family of 3 genera and ca. 50 species (Johnson 1993a). Three families of heterosporous water ferns occur in East TX (Azollaceae—Azolla, Marsileaceae—Marsilea, Pilularia, and Salviniaceae—Salvinia). These groups are quite distinct morphologically, and traditionally the marsileaceous (Marsilea and Pilularia) and salviniaceous (Azolla and Salvinia) lines were considered to have evolved independently from different homosporous fern ancestors. However, based on recent morphological, fossil, and molecular evidence, all three living heterosporous water fern families are considered to comprise a monophyletic group (Rothwell & Stockey 1994; Hasebe et al. 1995; Pryer 1999).