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• Marsileaceae
• Marsilea
• Marsilea quadrifolia

Marsilea quadrifolia — European water-clover

Facts

The leaves of water shamrock are divided into four segments that give it the appearance of a clover or shamrock. It is the only water shamrock in New England, and it was introduced from Europe into a lake in Connecticut in 1862.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams), shores of rivers or lakes

Characteristics

• Growth form

  Life form

  the plant is aquatic

  Life stage

  the plant is visible as a typical leaf-bearing fern (sporophyte)

  Spore-bearing leaflets

  the spore-bearing fronds are dramatically different from the sterile fronds

• Leaves

  Features of leaves

  there are no special features on the leaves

  Leaf blade length

  1.4–4.2 cm

  Leaf blade shape

  the leaf blades are roughly triangular

  Leaf blade tip shape

  the tip of the leaf blade is rounded

  Leaf blade width

  At least 1.2 cm

  Leaf divisions

  the leaf blade is compound (divided into leaflets)

  Leaf lifespan

  the leaves drop off in winter

  Leaf stalk hairs

  • the leaf stalk has hairs
  • there are no hairs on the leaf stalk

  Leaf stalk length

  54–165 mm

  Leaf stalk relative length

  the leaf stalk is more than three quarters as long as the blade

  Leaf stalk scale location

  there are no scales on the leaf stalk

  Leaf stalk scales

  there are no scales on the leaf stalk

  Leaf vein branching

  the secondary veins of the leaf blade split and rejoin to form a netlike pattern

  Leaf vein tips

  the veins go all the way to the edge of the leaf blade

  Lobe or leaflet length

  8–27 mm

  Lobe or leaflet pairs

  2

  Lobe or leaflet shape

  the lobe or leaflet is roughly triangular with the stalk in the center of the widest side (broad-triangular)

  Lobe or leaflet width

  8–27 mm

  Plant growth form

  the leaves float on the surface of the water

  final leaf segment margin

  the topmost lobe or leaflet of the leaf blade has a smooth or lobed edge

• Place

  Habitat

  aquatic

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • in lakes or ponds
  • in rivers or streams
  • shores of rivers or lakes

• Spores or spore cones

  Sorus features

  there are no special features on the sorus

  Sorus shape

  there are no sori, or they are concealed in leaf segments or hardened, capsule-like structures derived from a modified leaflet

  Sporangia location

  the spores are enclosed in a hardened, capsule-like structure (sporocarp)

  Sporangium type

  the sporangia are opaque without an annulus and usually without a stalk (leptosporangiate)

  Spore forms

  there are two different types of spores present

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae