Excerpts from Jim Conrad's
from the the March 23, 2009 Newsletter, issued from near Natchez, Mississippi:
Back in St. Catharine NWR, in clear pools of permanent water here and there you can find very interesting aquatic plants rooted in the mud. One of them is shown above.
That's a Water-Starwort, CALLITRICHE HETEROPHYLLA. In the picture, green rosettes floating atop the water's surface top vertical stems attaching to horizontal runners rooted in mud about ten inches below the water's surface. You can see that the plant's surface leaves have a different shape and color from those on submerged stems.
Native throughout North America and Mexico, this is one of those species with an enormous distribution, but in any particular place shows up only here and there. My impression is that it needs fairly unpolluted, undisturbed aquatic habitats, and of course such wetlands have suffered drastic loses. Though some authorities describe this as a common species, it's listed as threatened in Michigan and Wisconsin. It's a small plant, the larger leaves only about an inch long and the stems below the rosettes up to about a foot long. Water-Starworts are flowering plants, but the flowers and fruits are small, submersed and seldom noticed.
When you find pagodalike water-starworts rising through clear water populated with all kinds of microscopic aquatic invertebrates showing up brilliantly in intense sunlight, you're charmed by the three-dimensionality and liveliness of the scene. You wish you could be like water fleas and paramecia diving and soaring through the water like shooting stars. Few environments fill one with a sense of Nature being so healthily and beautifully Herself as clear-watered aquatic ones, and delicate little water-starworts are perfect citizens of that magical place.
The stems and fruits of starworts are grazed by ducks and other waterfowl. The branching stems provide shelter and forage to fish.