Hemianthus

Scientific name

Hemianthus Nutt.

Common names

baby’s tears, Nuttall's mud-flower, pearl grass

Family

Plantaginaceae

Similar genera

Elatine, Elodea, Hydrilla, Micranthemum, Rotala, Tonina

Native distribution

North America (two species), Caribbean

Species cultivated

Hemianthus callitrichoides Griseb.

H. glomeratus (Chapm.) Pennell

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
. Amphibiousamphibious:
(adj) of a plant able to live on land or in water
. Stem 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 3-4, 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, zygomorphiczygomorphic:
(adj) bilaterally symmetrical; symmetrical along only one plane
, short-pedicellate; sepals fused, lobes 4; corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube 1-lipped, abaxialabaxial:
(adj) the side facing away from the axis, as in the underside 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 is considered by some authorities as a synonym of Micranthemum. A fundamental difference between Hemianthus and Micranthemum is the corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube lobes; Hemianthus has a one-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 three lobedlobed:
(adj) divided into (usually rounded) segments
abaxialabaxial:
(adj) the side facing away from the axis, as in the underside of a leaf
lip, while Micranthemum has a two-lipped corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
tube with 3 adaxialadaxial:
(adj) pertaining to the side facing toward the axis, as in the upper surface of a leaf
lobes and two abaxialabaxial:
(adj) the side facing away from the axis, as in the underside of a leaf
lobes united, appearing as one lobe.