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• Dichotomous Key
• Poaceae
• Poaceae Group 5
• Taeniatherum
• Taeniatherum caput-medusae

Taeniatherum caput-medusae — Medusa-head

Facts

Medusa-head is a non-native grass that is considered a noxious weed in several western states, where it has invaded vast areas formerly dominated by native perennial grasses. In New England it is a rare visitor, having been collected only in Connecticut.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

• Flowers

  Anther length

  0–1 mm

  Anther number

  0–3

  Awn on glume

  the glume has an awn

  Bristles below spikelets

  no

  Floret lower bract texture

  the lemma is thin and flexible

  Floret number

  2–3

  Floret types within spikelet

  there are at least two distinct forms of florets within one spikelet

  Glume awn length

  5–80 mm

  Glume relative length

  neither glume is quite as long as all of the florets

  Glume veins

  • 1
  • 3

  Glumes per spikelet

  2

  Inflorescence axis hairs

  the inflorescence axis is smooth and has no hairs

  Inflorescence axis orientation

  the inflorescence axis is straight

  Inflorescence branch length

  0 cm

  Inflorescence branch roughness

  NA

  Inflorescence branches

  there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious

  Inflorescence branches coming off the lowest stem node

  0

  Inflorescence crowding

  NA

  Inflorescence length

  12–60 mm

  Inflorescence type (general)

  the inflorescence is a spike, or is spike-like, lacking obvious branches

  Inflorescence type (specific)

  the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)

  Inforescence position

  the spikelets are mainly carried at the end of the stem

  Lemma awn base

  the awn is attached right at the tip of the lemma

  Lemma awn coiled

  the lemma awn is straight or twisted, but not coiled one half turn

  Lemma awn length

  20–110 mm

  Lemma awn number

  the lemma has one awn on it

  Lemma awn orientation

  • the awn of the lemma is straight
  • the awn of the lemma on dried or older plants is curved or bent outwards

  Lemma cross-section

  the lemma is flat or rounded if you cut across the midpoint

  Lemma hairs

  the lemma is hairless between the veins

  Lemma keel hairs

  NA

  Lemma marginal vein hairs

  the marginal vein of the lemma is hairless

  Lemma surface

  the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)

  Lemma tip

  the lemma tip is a simple point, with or without an awn (long narrow extension ending in a point)

  Lemma tip shape

  the lemma tip tapers to a long narrow point (it may or may not also have an awn or teeth at the tip)

  Lemma vein number

  5

  Lemma vein orientation

  the veins on the lemma stay roughly parallel throughout

  Lower glume relative length

  the lower glume is nearly as long, or as long as, the upper glume

  One or more florets

  there is more than one floret per spikelet

  Palea length

  At least 0 mm

  Palea relative length

  palea is less than one half as long as lemma or absent

  Reproductive system

  all the flowers on the plant have both carpels and stamens (synoecious)

  Spikelet axis tip

  there is no extension of the spikelet axis beyond the tip of the spikelet

  Spikelet disintegration

  the spikelet breaks off above the glumes, so that after the florets fall off, the glumes remain

  Spikelet length

  6–12 mm

  Spikelet number per node

  Up to 4

  Spikelet pedicel

  the spikelets do not have pedicels

  Spikelet pedicel length

  0 mm

  Spikelet position

  NA

  Spikelet shape

  the spikelets are another shape in profile

  Spikelets per panicle branch

  0

  Spikelets spiny

  the spikelets do not appear spiny

  Tip of glume

  the tip of the glume is not divided (though it may have an awn on it)

  Upper glume relative length

  the upper glume is up to one half as long as the lowest lemma

  Upper glume shape

  the upper glume is widest at or below the middle

• Fruits or seeds

  Groove on seed

  the caryopsis has a groove running most of its length

  Seed length

  4–5.2 mm

• Growth form

  Horizontal rooting stem

  no

  Lifespan

  the plant lives only a single year or less

  Rhizomes

  no

  Roots

  there are only slender roots on the plant

• Leaves

  Leaf auricles

  • the leaves do not have auricles
  • the leaves have auricles

  Leaf basal lobe hairy

  the lobes at the base of the leaf blades are hairless

  Leaf blade cross-section

  • the leaf blade is clearly folded or rolled inwards
  • the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards

  Leaf blade hairs

  the leaf blade is hairy

  Leaf blade length

  3–12 cm

  Leaf blade texture

  • the leaf blade is rough and sandpapery
  • the leaf blade is smooth, or it may have soft hairs

  Leaf blade width

  0.2–2.5 mm

  Leaf ligule length

  0.2–0.6 mm

  Leaf ligule type

  the leaf ligule is in the form of a membrane

  Leaf margin glands

  there are no glands along the edges of the leaf blade

  Leaf sheath closed around stem

  the margins of the leaf sheath are overlapping and not fused together except in the basal half (or less)

  Leaf sheath hair type

  • there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases
  • there are no hairs on the surface of the leaf sheath

  Leaf sheath hairs

  • there are hairs on the surface of the leaf sheath
  • there are no hairs on the surface of the leaf sheath

  Orientation of topmost leaf

  • the flag leaf is held outward at more than a 45 degree angle from the stem, or it curves downwards from the horizontal
  • the flag leaf is held upright, or at less than a 45 degree angle out from the stem

• Place

  Habitat

  terrestrial

  New England state

  Connecticut

  Specific habitat

  man-made or disturbed habitats

• Stem, shoot, branch

  Plant height

  5–70 cm

  Stem hairs

  the stem is nearly to completely hairless

  Stem node number

  3–6

  Stem orientation

  • the stems are upright
  • the stems trail at the base, but turn upwards at the tips

  Stem spacing

  • the stems grow close together in compact clusters or tufts
  • the stems grow singly or a few together (they may form diffuse colonies)

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae