Micranthemum

Scientific name

Micranthemum Michx.

Common names

baby’s tears, shade mudflower, pearl grass

Family

Plantaginaceae

Similar genera

Bacopa, Callitriche, Elodea, Hemianthus, Lysimachia, Rotala

Native distribution

North and Central America, Caribbean

Species cultivated

Micranthemum umbrosum (J.F. Gmel.) S.F. Blake

M. tweediei Benth.

Adventive distribution

none

Weed status

not weedy

Habit

small, emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
and amphibiousamphibious:
(adj) of a plant able to live on land or in water
creeping stem plant

Brief description

Annual or perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
. Stem amphibiousamphibious:
(adj) of a plant able to live on land or in water
, creeping or ascending, rooted at nodes. Leaves oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, decussatedecussate:
(adj) arranged along stem in pairs, with each pair at right angles to the pairs above and below
or in whorls of 3 to 4, sessilesessile:
(adj) attached directly, without a stalk
; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
orbicular, obovateobovate:
(adj) ovate, with the narrow end at the base
to ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, venationvenation:
(n) the arrangement of veins in a leaf
indistinct; marginmargin:
(n) edge; rim
entireentire:
(adj) having a continuous margin that is not toothed or lobed
. Flowers minute, solitary, in leaf axils, zygomorphiczygomorphic:
(adj) bilaterally symmetrical; symmetrical along only one plane
, short-pedicellate; calyxcalyx:
(n) the outer whorl of the perianth; all the sepals of a flower
tubular, lobes 4; corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tubular, white, 2-lipped, abaxialabaxial:
(adj) the side facing away from the axis, as in the underside of a leaf
lip short, emarginateemarginate:
(adj) with a shallow notch at apex
, of 2 united lobes; adaxialadaxial:
(adj) pertaining to the side facing toward the axis, as in the upper surface of a leaf
lip 3-lobed; stamens 2-4. Dispersal by stem fragments or seed.

Natural habitat

bright sunlight, lakes, rivers, and streams; shallow water and muddy littorallittoral:
(adj) of or along the shore
zone

Additional comments

Hemianthus Nutt. is considered by some authorities as a synonym of Micranthemum, although it is often used in the aquarium trade. A fundamental difference between Hemianthus and Micranthemum is in the number of corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube lobes; Hemianthus has a 1-lipped corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube with adaxialadaxial:
(adj) pertaining to the side facing toward the axis, as in the upper surface of a leaf
lobes absent and a 3-lobed abaxialabaxial:
(adj) the side facing away from the axis, as in the underside of a leaf
lip, while Micranthemum has a 2-lipped corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube with three adaxialadaxial:
(adj) pertaining to the side facing toward the axis, as in the upper surface of a leaf
lobes and the two abaxialabaxial:
(adj) the side facing away from the axis, as in the underside of a leaf
lobes united, appearing as one lobe.