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• Haloragaceae
• Myriophyllum
• Myriophyllum tenellum

Myriophyllum tenellum — slender water-milfoil

Facts

Slender water-milfoil gets its common name from its slender, leafless stems, which differ from other milfoils whose stems are leafy. The flowers are wind pollinated, and the carpellate (seed-bearing) flowers mature before the staminate (pollen-bearing) flowers, thereby reducing the chance of self pollination.

Habitat

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

Characteristics

• Clonal plantlets

  Bulbils

  the plant does not appear to have bulbils

  Bulblets replace flowers

  there are no bulblets where the flowers are located

• Flowers

  Anther attachment

  the anther is attached by its base to the filament

  Anther color

  the anthers show no hint of a pink, reddish or purplish tint

  Anther length

  1.2–1.7 mm

  Anther opening

  the anthers have narrow slits or furrows that run lengthwise along the anthers

  Anther spurs

  the anthers do not have spurs on them

  Calyx growth after flowering

  • NA
  • the calyx grows to cover or partially cover the fruit

  Calyx symmetry

  there are two or more ways to evenly divide the calyx (the calyx is radially symmetrical)

  Carpels fused

  the carpels are fused to one another

  Cleistogamous flowers

  there are no cleistogamous flowers on the plan

  Corolla morphology

  NA

  Corolla palate

  no

  Corona lobe length

  0 mm

  Epicalyx

  the flower does not have an epicalyx

  Epicalyx number of parts

  0

  Filament surface

  the filament is smooth, with no hairs or scales

  Flower appearance

  the flowers appear after the leaves have appeared

  Flower description

  the flower has an inferior ovary, with or without a hypanthium

  Flower orientation

  the flower points upwards or is angled outwards

  Flower petal color

  • blue to purple
  • pink to red

  Flower reproductive parts

  • the flower has both pollen- and seed-producing parts
  • the flower has either only pollen- or only seed-producing parts

  Flower symmetry

  there are two or more ways to evenly divide the flower (the flower is radially symmetrical)

  Flowers sunken into stem

  no

  Form of style

  NA

  Fringed petal edges

  the petals are not fringed

  Fused stamen clusters

  NA

  Fusion of sepals and petals

  both the petals and sepals are separate and not fused

  Hairs on flower stalk

  NA

  Hairs on inflorescence

  the axis of the inflorescence has no hairs on it

  Horns in hoods (Asclepias)

  NA

  Hypanthium

  the flower does not have a hypanthium

  Hypanthium length

  0 mm

  Inflorescence length

  20–50 mm

  Inflorescence one-sided

  the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks

  Inner tepals (Rumex)

  NA

  Length of flower stalk

  0 mm

  Marks on petals

  there are no noticeable marks on the petals

  Nectar spur

  the flower has no nectar spurs

  Number of branches in umbel

  0

  Number of carpels

  0–4

  Number of pistils

  • 0
  • 1

  Number of sepals, petals or tepals

  there are four petals, sepals, or tepals in the flower

  Number of styles

  0

  Ovary position

  the ovary is below the point of petal and/or sepal attachment

  Petal and sepal arrangement

  the flower includes two cycles of petal- or sepal-like structures

  Petal and sepal colors

  • blue to purple
  • pink to red

  Petal appearance

  the petals are thin and delicate, and pigmented (colored other than green or brown)

  Petal base

  the petal narrows gradually or does not narrow at the base

  Petal folds or pleats

  the petals of the flower do not have folds or plaits

  Petal glandular dots or scales

  no

  Petal hairs (Viola)

  NA

  Petal length relative to sepals

  the petals are longer than the sepals

  Petal number

  4

  Petal shape

  • the petal outline is elliptic (shaped like an ellipse; widest near the middle and tapering at both ends)
  • the petal outline is oblong (rectangular, but with rounded ends)
  • the petal outline is obovate (roughly egg-shaped, but with the widest point above the middle of the leaf blade)

  Petal tip shape

  the petal tip is rounded

  Petal tips (Cuscuta)

  NA

  Raceme attachment (Veronica)

  NA

  Reproductive system

  • each flower has only carpels or only stamens, but both types of flower are present on each plant (monoecious)
  • the plant has flowers with both carpels and stamens, as well as flowers with only carpels or only stamens (polygamous)

  Scales inside corolla

  NA

  Sepal and petal color

  the sepals are different from the petals

  Sepal appearance

  the sepals are green or brown, and leaf-like in texture

  Sepal appendages

  the sepals do not have appendages on them

  Sepal appendages (Oenothera)

  NA

  Sepal auricles

  the sepals have no auricles

  Sepal number

  4

  Sepal uniformity

  all the sepals are about the same size

  Spur length

  0 mm

  Spur number

  NA

  Stamen appendages

  stamen appendages are absent

  Stamen attachment

  • the stamens are attached at or near the bases of the petals or tepals
  • the stamens are attached at or near the bases of the petals or tepals

  Stamen lengths differ

  the stamens are all approximately the same length

  Stamen morphology

  the stamens within each cycle are the same

  Stamen number

  • 0
  • 4

  Stamen relative length

  anything

  Stamens fused

  the stamens are not attached to one another

  Staminodes

  there are no staminodes on the flower

  Stigma length

  At least 0 mm

  Stigma position

  • NA
  • the stigmas are in another position

  Style length

  0 mm

  Style relative length

  NA

  Surface of ovary

  the ovary surface has no points, bumps or wrinkles

  Umbel flower reproductive parts

  NA

  Upper lip of bilabiate corolla

  NA

• Fruits or seeds

  Achene shape

  NA

  Achene surface (Polygonum)

  NA

  Berry color

  NA

  Capsule color (Viola)

  NA

  Capsule ribs

  NA

  Capsule splitting

  NA

  Fruit (pyxis) dehiscence

  NA

  Fruit beak length

  0 mm

  Fruit features (Brassicaceae)

  NA

  Fruit length

  1–1.2 mm

  Fruit length relative to sepals

  • NA
  • the fruit is about the same length as its associated sepals
  • the fruit is shorter than its associated sepals

  Fruit locules

  four

  Fruit shape

  the fruit is another shape than those described

  Fruit stalk orientation

  NA

  Fruit type (general)

  the fruit is dry but does not split open when ripe

  Fruit type (specific)

  the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)

  Hair type on fruit

  NA

  Hairs on fruit

  the fruits are not hairy

  Legumes (Fabaceae)

  NA

  Mericarp length

  1–1.2 mm

  Mericarp segment shape (Desmodium)

  NA

  Other markings on berry

  NA

  Ovary stipe

  the ovary or fruit does not have a stipe

  Ovary stipe length

  0 mm

  Placenta arrangement

  the plant has apical placentation, where one or a few ovules develop at the top of a simple or compound ovary

  Rows of seeds in fruit (Brassicaceae)

  NA

  Schizocarpic fruit compression

  the fruit is not flattened

  Schizocarpic fruit segments

  4

  Seed number

  4

  Seeds comose

  no hairs

  Septum in fruit (Brassicaceae)

  NA

  Wings on fruit

  the fruit does not have wings on it

  prickles on fruits

  the fruits do not have thorn-like defensive structures

• Glands or sap

  Glands on leaf blade

  • NA
  • the leaf blades do not have glandular dots or scales

  Sap

  the sap is clear and watery

  Sap color

  the sap is clear

• Growth form

  Growth form

  the plant is an herb (it has self-supporting stems)

  Horizontal rooting stem

  the plant does not have stolons

  Lifespan

  the plant lives more than two years

  Parasitism

  the plant is not parasitic

  Plant color

  the leaves or young stems of the plant are green

  Plants darken when dry

  no

  Spines on plant

  the plant has no spines

  Underground organs

  the plant has a rhizome (a horizontal underground stem with roots growing from it)

• Leaves

  Bracteole edges

  the bracteole margins are entire (without teeth, lobes or hairs)

  Bracteole number (Apiaceae)

  0

  Bracteole shape

  • the bracteoles are linear (very narrow, with more or less parallel sides)
  • the bracteoles are triangular (the base is on one of the three roughly straight sides)

  Bracteoles

  • the plant has bracteoles between the primary bracts and the flowers
  • there are no bracteoles on the plant

  Bracts in plantain (Plantago)

  NA

  Final leaf segment length (compound lvs only)

  0 mm

  Final leaf segment length to width ratio (compound lvs only)

  0

  Final leaf segment width (compound lvs only)

  0 mm

  Floral bract texture

  the floral bracts are green, with a leaf-like texture

  Floral bracts

  the flower has one or more bracts associated with it

  Flower bract length

  1–4 mm

  Hairs on leaf stalk

  NA

  Hairs on underside of leaf

  • NA
  • the underside of the leaf is not hairy, or it has very few hairs

  Hairs on upper side of leaf

  • NA
  • the upper side of the leaf is not hairy, or it has very few hairs

  Hooked hairs on underside of leaf

  NA

  Inflated hairs on leaf

  • NA
  • the leaf blade does not have inflated hairs on it

  Leaf arrangement

  • NA
  • alternate: there is one leaf per node along the stem

  Leaf blade base

  • NA
  • the leaf has no stalk

  Leaf blade bloom

  • NA
  • the underside of the leaf has no noticeable bloom

  Leaf blade edges

  • NA
  • the edge of the leaf blade is entire (has no teeth or lobes)

  Leaf blade hairs

  NA

  Leaf blade length

  At least 0 mm

  Leaf blade surface colors

  • NA
  • the upper side of the leaf blade is relatively uniform in color

  Leaf blade texture

  the leaf blade is herbaceous (has a leafy texture)

  Leaf blade width

  At least 0 mm

  Leaf duration

  • NA
  • the leaves drop off in winter (or they whither but persist on the plant)

  Leaf form

  the leaves are small and thin and lack leaf stalks

  Leaf hair orientation

  NA

  Leaf sheath length

  0 mm

  Leaf spines

  there are no spines on the leaf edges

  Leaf stalk

  the leaves have no leaf stalks, but attach directly to the stem

  Leaf stalk attachment to leaf

  NA

  Leaf stalk base

  NA

  Leaf stalk length

  0 mm

  Leaf teeth and lobes

  • NA
  • the edge of the leaf blade is entire (has no teeth or lobes)

  Leaf tufts in axils

  there are no clusters of smaller leaves growing out of axils

  Leaf type

  • NA
  • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

  Leaf types

  • NA
  • There is a gradual change in appearance of the leaves from the base (or near the base) of the plant to those from further up on the stem, with leaves progressively changing as one moves higher on the stem (often becoming shorter, or less toothed/lobed, and/or with shorter petioles).

  Leaf variation

  • NA
  • the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem

  Leaflet number

  0

  Leaflet petiolules

  NA

  Leaves per node

  • NA
  • there is one leaf per node along the stem

  Pinnately compound leaf type

  NA

  Specific leaf type

  • NA
  • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

  Stipels

  NA

  Stipule edges

  NA

  Stipule features

  NA

  Stipule fused to leaf stalk

  NA

  Stipule length

  0 mm

  Stipule shape

  NA

  Stipules

  there are no stipules on the plant

  Teeth per side of leaf blade

  0

• Place

  Habitat

  • aquatic
  • wetlands

  New England state

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

  Specific habitat

  • in lakes or ponds
  • shores of rivers or lakes

• Scent

  Plant odor

  the plant does not have much of a smell

• Stem, shoot, branch

  Branched tendrils

  NA

  Direction of stem hairs

  NA

  Flowering stem cross-section

  the flowering stem is circular, or with lots of small angles so that it is roughly circular

  Hair between stem nodes

  the stem has no hairs between the nodes

  Hairs between stem nodes

  NA

  Hooked hairs on stem between nodes

  no

  Leaves on stem

  • the flowering stem has no leaves above the base
  • there is at least one full leaf above the base of the flowering stem

  Length of hairs between stem nodes

  0 mm

  Plant height

  25–550 cm

  Stem bloom

  there is no powdery or waxy film on the stem

  Stem hair distribution

  NA

  Stem nodes swollen

  the stem is not swollen at the nodes

  Stem orientation

  • the stems are upright or angled outwards
  • the stems trail at the base, but may turn upwards at the tips

  Stem roughness between nodes

  the stem does not feel rough

  Stem spacing

  the plant is solitary, or a few plants are growing together

  Tendril origin

  NA

  Tendrils

  the plant does not have tendrils

  Wings on stem

  the stem does not have wings on it

Wetland status

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae