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• Podostemaceae
• Podostemum
• Podostemum ceratophyllum

Podostemum ceratophyllum — horn-leaved riverweed

Facts

Horn-leaved riverweed inhabits medium- to fast-flowing rivers bottoms with ledge, cobble or sand substrates. It is the only temperate North American species in a mainly tropical family (Podostemaceae), and is rare throughout New England, appearing on state endangered species lists in all states except New Hampshire. However, it may be more common than than this indicates, as riverbeds are likely under-botanized.

Habitat

Riverine (in rivers or streams), shores of rivers or lakes

Characteristics

• Clonal plantlets

  Turion length

  0 mm

• Flowers

  Carpels fused

  the carpels are fused to one another

  Flower lower lip length

  0 mm

  Flower number

  1

  Flower position

  • the flowers are above the surface of the water
  • the flowers are below the surface of the water

  Flower symmetry

  NA

  Inflorescence type

  • the flowers grow out of the axil (point where a branch or leaf is attached to the main stem)
  • the inflorescence has only one flower on it

  Inflorescence width

  Up to 2 mm

  Length of flower stalk

  Up to 10 mm

  Nectar spur

  the flower has no nectar spurs

  Number of carpels

  2

  Ovary position

  the sepals and/or petals are attached below the ovary

  Palate on corolla

  NA

  Petal and sepal arrangement

  the flower includes neither petals nor sepals

  Petal appearance

  NA

  Petal color

  NA

  Petal fringed edges

  NA

  Petal fusion

  NA

  Petal hairs on inner/upper surface

  NA

  Petal length

  0 mm

  Petal number

  0

  Petal or sepal number

  there are no petals, sepals, or tepals in the flower, or they are not clearly present

  Pistil number

  1

  Sepal appearance

  NA

  Sepal length

  0 mm

  Sepal number

  0

  Sepals fused only to sepals

  NA

  Spur length

  0 mm

  Stamen number

  1 or 2

  Stamen position relative to petals

  NA

  Stamens fused

  the stamens are fused to one another at or near their bases

  Stamens fused to petals

  the stamens are not fused to the petals or tepals

  Style length

  0.5–1 mm

  Style number

  2

• Fruits or seeds

  Fruit length

  2.5–3 mm

  Fruit type (general)

  the fruit is dry and splits open when ripe

  Fruit type (specific)

  the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)

• Glands or sap

  Oil glands on nodes

  none of the nodes have oil glands

  Sap

  the sap is clear and watery

• Growth form

  Lifespan

  the plant lives more than two years

  Root septa

  the roots do not have transverse septa

  Roots floating in water

  there are no clusters of roots floating in the water

  Turions

  there are no turions on the plant

  Underground organs

  there are only slender roots on the plant

• Leaves

  Bract position (Sparganium)

  NA

  Bract relative length

  At least 1379 mm

  Bracts

  the flowers or their pedicels have bracts at their bases

  Floating leaf basal lobes

  NA

  Floating leaf blade width

  0 mm

  Floating leaf length

  0 mm

  Floating leaf shape

  NA

  Floating leaf tip

  NA

  Floral bract form

  the bracts are much more lobed, or much less lobed, than the foliage leaves

  Floral bract length

  2–3 mm

  Leaf arrangement

  alternate: there is one leaf per node along the stem

  Leaf position

  the leaves are all submerged underwater

  Leaf special features

  none of the mentioned special features are present

  Leaf-like branch segments

  0

  Leaf-like branch shape

  NA

  Specific leaf type

  • the leaf is divided into two equal parts; these parts may also be divided into two further parts
  • the leaf is not divided, rather the blade is made up of one segment

  Staminate bract edge (Myriophyllum)

  NA

  Stipules

  the plant has stipules

  Trap-bladder length

  0 mm

  Underwater leaf blade edges

  • the underwater leaf blades are lobed
  • the underwater leaf has smooth edges, without teeth

  Underwater leaf blade shape

  • the underwater leaf blade is capillary (very fine and hair-like)
  • the underwater leaf blade is linear (very narrow with more or less parallel sides)

  Underwater leaf stalk

  yes

  Veins in floating leaf

  0

• Place

  Habitat

  aquatic

  New England state

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

  Specific habitat

  • in rivers or streams
  • shores of rivers or lakes

• Stem, shoot, branch

  Flowering stem growth form

  • the flowering stem is upright
  • the flowering stem trails along the substrate, or floats in the water

Wetland status

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae