“The rapid development, as far as we can judge,
of all the higher plants within recent geological time
is an abominable mystery.” ~Darwin
Last night I enjoyed Woody Allen’s film, “Midnight in Paris,” a surrealistic journey into the past. Cinematic stills of Paris open a dreamy storyline, in which the protagonist, a writer searching for his voice among his literary and artistic idols, finds inspiration strolling through the city at midnight. In one scene, he stands before Monet’s famous paintings of water lilies. Gazing at those water lilies transports him back in time.
Water lilies are decedents of the most archaic of the flowering aquatic plant world. Fossils of earlier versions of these aquatic plants are evidence of their great age. By the mid-Cretaceous period, angiosperms dominated the planet. Water lilies were among the earliest fossil flowers found. Basal angiosperms including water lilies such as Nymphaea, Brasenia, Nuphar remind us of a deep evolutionary past of the flowering aquatic plants. In 1904, Ohio State University botanist J.H. Schaffner asserted that water lilies are the very “stock” from which all flowering plants stem. This belief wasn’t readily embraced by other scientists of his time but his observations about Nymphaea were later confirmed.
Those who study aquatic plants even today will admit they are difficult subjects with converging and evolving morphology. “Precise clues to Darwin’s ‘abominable mystery,’ the origin of flowering plants, have eluded systematists for more than a century,” according to authors of a study on the “Molecular evolutionary history of ancient aquatic angiosperms.” (Les, Garvin, et.al. 1991) There are lots of unanswered mysteries surrounding water lilies in particular, for instance, whether they are monocots or dicots. There are differing viewpoints among scientists. Water lilies are simply an unusual group of plants. The origin of angiosperms (flowering plants) is at the heart of Darwin’s “abominable mystery.” Darwin, along with many scientists after him, have sought to answer questions about the rise of flower-frequenting insects and the origins of certain plants on isolated islands.
Water quality monitors can look for certain aquatic plants as ecological indicators. A quick Google search for “water quality” will reveal that water lilies are often used as symbols for ‘good water quality’ if only because they are hardy aquatic plants and thrive in freshwater lands, ponds and wetlands. However, they are native to the eastern U.S. and were introduced to the western states in the early 1800s. In some areas, water lilies have been regarded as an invasive (or) non-native species. For example, here is a King County, WA fact sheet on non-native water lilies and management of them as an invasive species: http://your.kingcounty.gov/dnrp/library/water-and-land/weeds/Brochures/Fragrant-Water-Lily-Fact-Sheet.pdf and Non-native freshwater plants on the Washington State Dept of Ecology website (a fact sheet on Nymphaea odorata including habits, pollination strategy, uses by Native Americans, status as introduced plant.)
Ferns are also considered “dinosaurs” of the plant world. Aquatic floating ferns, such asAzolla, a tiny water fern, also called mosquito fern; Marsilea, also called water clover;and Salvinia, a water fern native to tropical America, are unusual since most types of ferns are terrestrial, not aquatic. Floating ferns are heterosporous, which makes them the most advanced type of fern. Just think—there are around 9000 species of living ferns and fewer than 1% produce spores (similar to seeds). This is true of the water ferns with the genus of Azolla, Marsilea and Salvinia.
Mosquito ferns can be aggressive invasives—quickly covering the surface of a quiet pond, providing habitat for macroinvertebrates, a food source for reptiles and amphibians. But if the little fern, which can be green or reddish in color, covers the surface of the whole pond, it can deplete the oxygen and lead to fish kills. Surprisingly, because of its aggressiveness, mats of azolla can reduce the occurrence of harmful algae blooms and limit the growth of exotic aquatic plants, such as water hyacinth. For more about azolla water ferns, go to: http://waynesword.palomar.edu/plnov98.htm
About ten species exist within the Salvinia genus. Related to the azolla water fern,Salvinia floating ferns have unique abaxial leaves (facing away from the plant) and creeping stems, but no true roots. Giant Salvinia is native to South America and an introduced, invasive species here in the U.S., including Louisiana lakes and Florida.http://plants.ifas.ufl.edu/node/395
Water clover looks like four-leaf clover only it’s a floating fern in the Marsilea genus. It spreads by a thin hair-like underwater rhizome structure. Of all the floating ferns,Marsilea is the most species-rich with between 45-65 species.http://www.plantoftheweek.org/week347.shtml There are a number of great books available on aquatic plants, including Fern Ecology Ed. Klaus Mehltreter, et.al. (2010) and A Manual of Aquatic Plants by Norman Fassett (2006). 
For these and other wetland ecology books, visit the Wetland Bookshelf:http://www.aswm.org/wetlands/wetland-bookshelf/1333-wetland-science-ecology-books
But what inquiring minds want to know…is the four-leafed water clover lucky? It’s become a popular plant to grow in garden pools (because it is so easy to manage) and even brought inside as a houseplant! At least one blogger calls it the “lucky charm” of the pond: http://www.dragonflyaquatics.com/blog/
2009/03/water-clover/
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