Kingdom: Plantae
Division: Pteridophyta (Filicophyta)
Class: Pteridopsida (Filicopsida)
Order: Marsileales
Family: Marsileaceae
Marsilea L., Spec. Plant. 2:1099, 1753.
Marsilea is a curious group of ferns that to the uninitiated mimics four-leaved clovers. All members of the genus have four more or less equal pinnae that appear to radiate from a central point, but are clearly pinnate on close examination.
Like Salvinia and Azolla, Marsilea is heterosporous. Heterospory in these groups is clearly an adaptation to an aquatic environment. Recent studies have shown that, despite their morphological differences, the three groups of water ferns are monophyletic. Unlike Salvinia or Azolla, Marsilea has retained circinate vernation.
Marsilea plants may grow in water, with leaf blades floating on the surface, or they may grow in mud or moist soil. They have cord-like, long-ranging rootstocks.
Marsilea plants are sometimes grown in small ponds, but since fish enjoy eating the plants, they generally don't last long in the presence of fish.
Known chromosome counts for the genus are n=16, n=20, n=22, n=30, and n=32. The n=32 is undoubtedly a doubling from n=16. n=20 was probably the original number of the current-day genus, derived from a doubling of n=10, which in turn was derived by a reduction from n=11. n=16 and n=22 are probably derived from n=20, while n=30 would have been a hybrid derivation from n=20.
Species of Marsilea:
Subgenus Marsilea
Subgenus Clemys
Subgenus Nodorhizae
Subgenus Distorta
Subgenus Gymnocarpa
Subgenus Aegyptica
Subgenus Drummondii
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This page was last revised on 11-20-1997.