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• Desmodium sessilifolium

Desmodium sessilifolium — sessile-leaved tick-trefoil

Facts

Sessile-leaved tick-trefoil is at the northeastern limit of its range in New England, and is very rare in our region. The slightly misleading name refers not to the absence of petioles, but to the very short petioles (1-3 mm in most cases) possessed by this species.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields, sandplains and barrens

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 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 symmetry

  there is only one way to evenly divide the calyx (the calyx is bilaterally symmetrical)

  Carpels fused

  • NA
  • the carpel is solitary or (if 2 or more) the carpels are not 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 description

  the flower has a superior ovary and a hypanthium

  Flower length

  Up to 5 mm

  Flower petal color

  • blue to purple
  • pink to red

  Flower reproductive parts

  the flower has both pollen- and seed-producing parts

  Flower symmetry

  there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)

  Flowers sunken into stem

  no

  Form of style

  the style is narrow at the tip and unbranched

  Fused stamen clusters

  there are two clusters of fused stamens

  Fusion of sepals and petals

  the petals or the sepals are fused into a cup or tube

  Hairs on flower stalk

  the flower stalk has hairs on it

  Hairs on inflorescence

  the axis of the inflorescence has hairs entirely without glands

  Horns in hoods (Asclepias)

  NA

  Hypanthium

  the flower has a hypanthium

  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

  Interior flower disk

  the flower does not have an interior disc

  Length of flower stalk

  1.5–4.5 mm

  Nectar spur

  the flower has no nectar spurs

  Number of carpels

  1

  Number of pistils

  1

  Number of sepals, petals or tepals

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

  Number of styles

  1

  Ovary position

  the ovary is above 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 folding in bud

  the petals in bud are arranged in a cycle with edges overlapping like roof shingles (imbricate)

  Petal folds or pleats

  • the petals of the flower do not have folds or plaits
  • the petals of the flower have folds or plaits on them

  Petal hairs (Viola)

  NA

  Petal length

  4–6 mm

  Petal length relative to sepals

  the petals are longer than the sepals

  Petal number

  5

  Petal tips (Cuscuta)

  NA

  Raceme attachment (Veronica)

  NA

  Reproductive system

  all the flowers have both carpels and stamens (synoecious)

  Scales inside corolla

  no

  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 color

  green to brown

  Sepal number

  4–5

  Sepal orientation

  the sepals are slightly curved outwards from the corolla

  Sepal relative length

  the sepal lobes are longer than the fused portion

  Sepal texture

  the sepals are either very thin but flexible, like a membrane, or they are leaf-like in texture

  Sepal uniformity

  one or more of the sepals is much narrower or shorter than the others

  Sepals fused only to sepals

  the sepals are fused to each other (not other flower parts), at least near their bases

  Stamen morphology

  the stamens within each cycle are the same

  Stamen number

  10

  Stamens fused

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

  Staminodes

  there are no staminodes on the flower

  Style petal-like

  the styles are not petal-like

  Umbel flower reproductive parts

  NA

  Upper lip of bilabiate corolla

  NA

• Fruits or seeds

  Achene relative orientation

  NA

  Achene shape

  NA

  Achene surface (Polygonum)

  NA

  Achene type

  NA

  Berry color

  NA

  Capsule color (Viola)

  NA

  Capsule ribs

  NA

  Capsule splitting

  • NA
  • the capsule splits by two main valves, teeth or pores

  Fruit (pyxis) dehiscence

  NA

  Fruit cross-section

  the fruit is at least somewhat flattened

  Fruit features (Brassicaceae)

  NA

  Fruit locules

  one

  Fruit shape

  the fruit is flat or strongly compressed

  Fruit stalk orientation

  the fruits point upward or spread or curve outward

  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

  the hairs on the fruits are simple (not branched), don’t have glands, and are not woolly

  Hairs on fruit

  the fruits have hairs on them

  Legumes (Fabaceae)

  the legume has none of the mentioned special features

  Mericarp length

  4–6.5 mm

  Mericarp segment shape (Desmodium)

  the mericarp is rounded on the lower margin

  Other markings on berry

  NA

  Ovary stipe

  the ovary or fruit has a stipe

  Ovary stipe length

  1–3 mm

  Placenta arrangement

  the plant has parietal placentation, where ovules develop on the wall or slight outgrowths of the wall forming broken partitions within a compound ovary

  Rows of seeds in fruit (Brassicaceae)

  NA

  Schizocarpic fruit compression

  the fruit is flattened perpendicular to the commissure

  Schizocarpic fruit segments

  1–3

  Seed number

  1–3

  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

  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)

  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

  NA

• Leaves

  Bracteole number (Apiaceae)

  0

  Bracteoles

  there are no bracteoles on the plant

  Bracts in plantain (Plantago)

  NA

  Final leaf segment length (compound lvs only)

  30–70 mm

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

  3–10

  Final leaf segment width (compound lvs only)

  5–15 mm

  Floral bracts

  the flower has one or more bracts associated with it

  Hairs on underside of leaf

  the underside of the leaf is fuzzy or hairy

  Hairs on upper side of leaf

  the upper side of the leaf is fuzzy or hairy

  Hooked hairs on underside of leaf

  yes

  Leaf arrangement

  alternate: there is one leaf per node along the stem

  Leaf blade base

  • the leaf has a distinct leaf stalk (petiole)
  • the leaf has no stalk

  Leaf blade base shape

  the base of the leaf blade is rounded

  Leaf blade base symmetry

  the leaf blade base is symmetrical

  Leaf blade edges

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

  Leaf blade hairs

  the leaf blade has simple hairs with no glands, and not tangled or wooly

  Leaf blade primary vein pattern

  the secondary veins branch off at intervals from the primary vein

  Leaf blade shape

  • the leaf blade is elliptic (widest near the middle and tapering at both ends)
  • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
  • the leaf blade is oblong (rectangular but with rounded ends)

  Leaf blade surface colors

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

  Leaf blade texture

  the leaf blade is coriaceous (has a firm, leathery texture)

  Leaf blade vein pattern

  the major veins form a net-like pattern due to splitting and rejoining

  Leaf blade veins

  the leaf blade has one main vein running from the base towards the tip (it may or may not have secondary veins)

  Leaf duration

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

  Leaf form

  the leaves are green, with an expanded blade and a leaf-like texture

  Leaf hair orientation

  • the hairs are flat against the leaf surface, mostly pointing towards the leaf tip
  • the hairs are standing up straight or curved in different directions

  Leaf shiny

  the upper side of the leaf is dull or slightly shiny

  Leaf spines

  there are no spines on the leaf edges

  Leaf stalk

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

  Leaf stalk attachment to leaf

  the petiole attaches at the basal margin of the leaf blade

  Leaf stalk base

  the petiole base is narrow where it attaches to the stem

  Leaf stalk length

  1–4 mm

  Leaf teeth and lobes

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

  Leaf tip

  • the tip of the leaf blade is acute (sharply pointed)
  • the tip of the leaf blade is obtuse (bluntly pointed)

  Leaf type

  the leaves are compound (made up of two or more discrete leaflets

  Leaf types

  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

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

  Leaflet number

  1–3

  Leaflet petiolules

  the leaflets of the compound leaf have petiolules

  Leaves per node

  there is one leaf per node along the stem

  Pinnately compound leaf type

  the pinnately compound leaves have a terminal leaflet (and usually have an odd number of leaflets per axis)

  Specific leaf type

  the leaf has a row of two or more lobes on each side of the central axis

  Stipels

  the petiolules have stipels at their bases

  Stipule features

  NA

  Stipule length

  3–5 mm

  Stipule shape

  the stipules are lanceolate (lance-shaped; widest below the middle and tapering at both ends)

  Stipules

  the plant has stipules

  Teeth per side of leaf blade

  0

• Place

  Habitat

  terrestrial

  Specific habitat

  • man-made or disturbed habitats
  • meadows or fields
  • sandplains or barrens

• Scent

  Plant odor

  the plant does not have much of a smell

• Stem, shoot, branch

  Branched tendrils

  NA

  Direction of stem hairs

  the hairs point mostly upwards to outwards

  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 hairs between the nodes

  Hairs between stem nodes

  the hairs on the stem are plain, without glands or branches, and not tangled

  Hooked hairs on stem between nodes

  yes

  Leaves on stem

  there is at least one full leaf above the base of the flowering stem

  Plant height

  60–150 cm

  Stem bloom

  there is no powdery or waxy film on the stem

  Stem nodes swollen

  the stem is not swollen at the nodes

  Stem orientation

  the stems are upright or angled outwards

  Stem spacing

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

  Stem succulence

  the stems are not succulent

  Tendril origin

  NA

  Tendrils

  the plant does not have tendrils

  Wings on stem

  the stem does not have wings on it

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae