Crystalwort family (Ricciaceae)
This is either a floating-aquatic or a
stranded-terrestrial plant. The thallus (undifferentiated body) of the
floating-aquatic form is 5-15 mm. across and about 1 mm. deep,
consisting of 1-3 primary lobes. Each primary lobe often divides
into 2 secondary lobes, forming a Y-shape. A smaller tertiary
lobe often develops where the secondary lobes diverge; it is usually
or heart-shaped. On the upper surface of the thallus, a narrow furrow
runs along the middle of each primary lobe. This furrow then divides to
run along the middle of each secondary lobe. When a tertiary lobe is
present, the furrow of the primary lobe is continued along its middle.
The tips of the secondary and tertiary lobes are rounded and notched.
The upper surface of a young thallus is light to medium green and
glabrous; it becomes more white with age. On the lower surface of the
floating-aquatic form of the thallus, there are abundant scales. These
are 2-10 mm. long, linear-lanceolate to lanceolate in shape,
membranous, and purplish; they are wider at their bases than their tips.
The thallus of a stranded-terrestrial plant is similar to the
floating-aquatic form of the thallus, except the former is more
branched and it tends to form a rosette-like shape up to 20 mm. across.
The lower side of the thallus for stranded-terrestrial plants has far
fewer purplish scales and they are much shorter in length. In contrast
to the floating-aquatic form, the lower side of the thallus of
stranded-terrestrial plants develops short
peg-like rhizoids and long smooth rhizoids. The peg-like rhizoids absorb moisture from the
ground, while the smooth rhizoids anchor the entire plant to the ground.
For both forms of this plant, there is a faint reticulated network on
the upper surface of the thallus (visible with 10x hand lens). In the
middle of each polygonal section of this network, there is a single
chambered air pore and several layers of minute air bubbles (visible
magnification). The floating-aquatic form of this plant reproduces
asexually during the growing season by breaking apart into 2 or more
smaller plants as the older lobes decay. The
stranded-terrestrial form of this plant is able to reproduce asexually
overwinters and all but its growing tips decay. These growing tips
float to the surface of the water during spring rains of the following
year, forming several new plants.
Sexual reproduction can occur when
this plant occurs in bodies of
temporary water (seasonal ponds, vernal pools, and other temporary
wetlands). Because this
plant is monoecious, both antheridia (male reproductive organs) and
archegonia (female reproductive organs) develop within the same
thallus. Spores are formed when the eggs of the archegonia are
fertilized by the sperm of the antheridia. Individual spores are about
50 micrometers across, black, and spiny. The spores are released from
the thallus as its older lobes decay; they are distributed in part by
water. However, the spores do not
germinate until at least a year after their release; this
usually occurs during the spring.
The preference is full sun to light shade, shallow water or wet
conditions, and soil containing sandy silt, sand with decaying organic
matter, or mud. This plant is a floating aquatic on surface water, it
also adapts to wet shorelines. It remains green throughout the growing
season, but turns black and has a tendency to disappear during winter.
Both slowly moving water and stagnant water are tolerated.
& Habitat: Fringed Heartwort (Ricciocarpos
natans) occurs occasionally throughout
Illinois, where it is native (see Distribution
It is widely
distributed in the United States and Canada, and it also occurs in
Europe. In Illinois, habitats include typical ponds and sandy ponds,
limestone sinkholes, shorelines of small lakes, shorelines and banks of
rivers, open water and shorelines of strip mine impoundments, mudflats
in rivers, vernal pools in wooded areas, puddles and muddy areas of
floodplain woodlands near rivers, oak flatwoods that flood
intermittently, open water and wet ground in swamps (including Bald
Cypress swamps), fallen logs in swamps, and wet willow thickets.
Fringed Heartwort is found in average to high quality wetland areas
where there are either permanent or temporary bodies of water,
especially in sandy areas. It is less common in degraded wetland sites.
Associations: Information about
floral-faunal relationships for
Fringed Heartwort (Ricciocarpos natans) is limited.
In Sweden, Mallard ducks used
this plant as a source of food (Hartman, 1985). Mallards and other
ducks probably feed on it in North America. Some turtles may
feed on this plant as well. Waterfowl, including ducks and geese, may
help to spread the spores of this plant to new wetland areas as the
spores may cling to their muddy feet and other body parts. The long
membranous scales of this plant in its floating form
provide cover and protection for various small aquatic invertebrates.
Location: Shoreline of an open body of water in
a sandy swamp at the
Heron County Park in Vermilion County, Illinois.
Fringed Heartwort (Ricciocarpos natans)
is a thalloid liverwort. Like the mosses, it is a non-vascular plant.
The appearance of this plant is similar to several Crystalwort species (Riccia
except it forms purplish scales and sometimes rhizoids along its
underside. Another difference is the presence of several layers of
minute air bubbles in the thallus. Most Crystalworts are terrestrial
species that are found in drier areas, although Floating Crystalwort (Riccia
is an exception. This latter species lacks furrows on the upper side of
its thallus and its lobes are more narrow than those of Fringed
Heartwort. Thus, it is not difficult to distinguish between them. Other
common names of Ricciocarpos natans are Purple-fringed
Riccia and Floating Liverwort. A common misspelling of the scientific
name is Ricciocarpus natans. An obsolete scientific
name for this species is Riccia natans.