Hydrocharitaceae

Taxonomy

Family name: Hydrocharitaceae A.L. Jussieu

Synonym(s): Blyxaceae Nakai; Elodeaceae Dumort.; Enhalaceae Nakai; Halophilaceae J. Agardh; Najadaceae Juss., nom. cons.; Stratiotaceae Schultz Sch.; Thalassiaceae Nakai; Vallisneriaceae Dumort.

Common name(s): tape-grass family

*Number of genera/species: 16/135

List of genera records in GRIN-Global

Disseminule

fruit (dehisced or indehiscentindehiscent:
not opening on its own, as in a fruit
) or seed

Description

Fruit dehiscentdehiscent:
(v. dehisce) splitting open at maturity to release contents (of a fruit)
, folliclefollicle:
a dry to (rarely) fleshy fruit derived from a single carpel that opens along a single longitudinal suture; the seeds may be arillate or with a fleshy testa
or septicidalsepticidal:
type of capsular dehiscence, opening longitudinally by separating between the septa of adjacent carpels
capsulecapsule:
a dry, dehiscent fruit formed by two or more carpels
, or indehiscentindehiscent:
not opening on its own, as in a fruit
, berryberry:
an indehiscent, fleshy fruit with one or a few to many seeds. The flesh may be homogenous throughout. Or, if the outer part is hard, firm, or leathery, referred to as an hesperidium. Septa are present in some, and the seeds may be arillate or with a fleshy testa.
or acheneachene:
a dry, indehiscent, one-seeded fruit, with seed attached to pericarp at a single point
(Najas), 8–100 mm long, globoseglobose:
3D shape—more or less spherical
to linearlinear:
(shape) long, narrow, and uniform in width; (of embryo) embryo is straight and much longer than wide
, roundround:
2D shape—orbiculate; circular
in transectiontransection:
a cross section; representing a plane made by cutting across an organ at a right angle to its length
, sometimes with persistent stylestyle:
in a flower, the narrow and elongated part of the pistil between the stigma and the ovary; sometimes persisting in fruit
and beakedbeaked:
a usually firm, terminal appendage, sometimes tapered
(Halophila), one to many seeded. Pericarppericarp:
fruit wall or fruit coat
green, white, yellow, or red, dulldull:
reflecting only a low proportion of incident light, with no apparent sheen
, fleshyfleshy:
texture—fairly firm and dense, juicy or at least moist, and easily cut
, chartaceouschartaceous:
=papery, papyraceous
(Najas), or membranousmembranous:
texture—extremely thin, pliable, and fairly tough
, smooth, spinyspiny:
having slender, stiff, sharp projections oriented in the general plane of the structure
or reticulatereticulate:
surface relief—netted, raised walls or concave grooves forming a net-like surface pattern with flat, concave, or convex interspaces
, sometimes pubescentpubescent:
surface relief—bearing hairs
. Fruits usually submerged.

Seed angularangular:
2D shape—having sides that meet at acute or obtuse angles  
to oblongoblong:
2D shape—much longer than broad with nearly parallel sides, corners are rounded
including C-shapedC-shaped:
2D-shape—semiannulate, curved into the shape of the letter 'C'
(some species of Najas), tereteterete:
approximately circular in cross section; width and thickness approximately equal
in transectiontransection:
a cross section; representing a plane made by cutting across an organ at a right angle to its length
, sometimes with conspicuous rapheraphe:
a ridge or seam on the seed coat, formed by the portion of the funiculus united to the ovule wall in longitudinally curved ovules
, 0.2–6 mm long. Seed coat brown or green, shinyshiny:
uniformly reflecting a high proportion of incident light at all angles
or dulldull:
reflecting only a low proportion of incident light, with no apparent sheen
, hard and thinthin:
having or being of relatively little depth
, smooth or variously sculptured, sometimes pubescentpubescent:
surface relief—bearing hairs
(Apalanthe, Vallisneria). Smooth seeds often disperse singly while sculpted seeds disperse together.

Embryo well developed (usually with large hypocotylhypocotyl:
portion of the embryonic axis below the cotyledons and above the radicle
and radicleradicle:
the embryonic root of the embryo
), often fills seed coat, linearlinear:
(shape) long, narrow, and uniform in width; (of embryo) embryo is straight and much longer than wide
, usually straight (curved in Halophila), often with several leaves at germination (Najas, Ottelia, Stratiotes). Hypocotylhypocotyl:
portion of the embryonic axis below the cotyledons and above the radicle
often with unicellular hairs. Endospermendosperm:
nutritive starch- and oil-containing tissue present in many seeds
scanty (Ottelia) or absent.

Identification features

Fruit
Type	berry, capsulecapsule: a dry, dehiscent fruit formed by two or more carpels , acheneachene: a dry, indehiscent, one-seeded fruit, with seed attached to pericarp at a single point , follicle
Size range	8–100 mm long
Shape(s)	globose, linearlinear: (shape) long, narrow, and uniform in width; (of embryo) embryo is straight and much longer than wide , ovoidovoid: 3D shape—ovate , cylindricalcylindrical: 3D shape—a cylinder, with parallel sides and a circular cross-section; tubular or rod-shaped , ellipsoid
Texture	fleshy, membranousmembranous: texture—extremely thin, pliable, and fairly tough , chartaceous
Surface relief	smooth or spinyspiny: having slender, stiff, sharp projections oriented in the general plane of the structure , reticulatereticulate: surface relief—netted, raised walls or concave grooves forming a net-like surface pattern with flat, concave, or convex interspaces , sometimes pubescent
Color(s)	green, red, yellow, white
Seed
Size range	0.2–6 mm long
Shape(s)	C-shaped, globoseglobose: 3D shape—more or less spherical , ovoidovoid: 3D shape—ovate , fusiformfusiform: spindle-shaped; broadest at the middle and tapering at both ends , straight, irregular, ellipsoidellipsoid: 3D shape—elliptic , polygonalpolygonal: =angular , oblong
Surface relief	smooth, reticulatereticulate: surface relief—netted, raised walls or concave grooves forming a net-like surface pattern with flat, concave, or convex interspaces , areolate, papillatepapillate: surface relief—bearing minute, distinct, broad-based projections, tapering to a rounded apex , spinyspiny: having slender, stiff, sharp projections oriented in the general plane of the structure , pittedpitted: surface relief—surface with small depressions in which the areas between the hollows do not take on the appearance of a true reticular net , with hookswith hooks: bristles or spines with curved or backwards pointing tips, or with secondary bristles along their length , sometimes pubescent
Color(s)	brown, green
Unique features	Smooth or highly sculpted seeds with large embryos that often fill seed coat.
Other
Embryo	well developed (usually with large hypocotylhypocotyl: portion of the embryonic axis below the cotyledons and above the radicle and radicleradicle: the embryonic root of the embryo ), fills seed coat, linearlinear: (shape) long, narrow, and uniform in width; (of embryo) embryo is straight and much longer than wide , usually straight (curved in Halophila), often with several leaves at germination (Najas, Ottelia, Stratiotes). Hypocotylhypocotyl: portion of the embryonic axis below the cotyledons and above the radicle often with unicellular hairs.
Nutritive Tissue	endosperm endosperm: nutritive starch- and oil-containing tissue present in many seeds absent

Distribution

Worldwide distribution in marine and freshwater environments.

Distribution map courtesy of Angiosperm Phylogeny Website.

References

Baskin and Baskin 2021Baskin and Baskin 2021:
Baskin C and Baskin J. 2021. Relationship of the lateral embryo (in grasses) to other monocot embryos: A status up-grade. Seed Science Research 31 (3): 199-210. doi:10.1017/S0960258521000209; Dahlgren et al. 1985Dahlgren et al. 1985:
Dahlgren RMT, Clifford HT, and Yeo PF. 1985. The families of the monocotyledons: structure, evolution, and taxonomy. Springer-Verlag, Berlin. 520 pp.; Flora of Australia 2021+Flora of Australia 2021+:
Flora of Australia. Australian Biological Resources Study, Canberra. Accessed January-May 2021. URL: http://www.ausflora.org.au; Flora of North America Editorial Committee 1993+Flora of North America Editorial Committee 1993+:
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 22+ vols. Flora of North America Association, New York and Oxford. Accessed January-December 2021. URL: http://beta.floranorthamerica.org.; Kirkbride et al. 2006Kirkbride et al. 2006:
Kirkbride JH, Jr, Gunn CR, and Dallwitz MJ. 2006. Family guide for fruits and seeds, vers. 1.0. Accessed September 2020ndash;January 2022. URL: https://nt.ars-grin.gov/seedsfruits/keys/frsdfam/index.cfm .; Kubitzki et al. 1990+Kubitzki et al. 1990+:
Kubitzki K et al., eds. 1990+. The families and genera of vascular plants. 7+ vols. Berlin etc.; Martin and Barkley 1961Martin and Barkley 1961:
Martin AC and Barkely WD. 1961. Seed Identification Manual. Universisty of California Press, Berkeley and Los Angeles, CA, USA. 220 pp.; Stevenson and Loconte 1995Stevenson and Loconte 1995:
Stevenson DW and Loconte H. 1995. A cladistic analysis of monocot families. In: Rudall PJ, Cribb PJ, Cutler DF, and Humphries CJ, eds. Monocotyledons: Systematics and Evolution. Royal Botanic Gardens, Kew.; Thiele and Adams 2014Thiele and Adams 2014:
Thiele KR and Adams LG. 2014. Families of Flowering Plants of Australia. Accessed January-December 2021. URL: https://keys.lucidcentral.org/keys/v3/FFPA/key/FFPA/Media/Html/index.htm; Zhengyi et al. 2004+Zhengyi et al. 2004+:
Zhengyi W, Raven PH, and Deyuan H. 2004+. Flora of China [online]. 25 vols. Science Press, Beijing China amp; Missouri Botanical Garden, St. Louis USA. Accessed January-December 2021. http://flora.huh.harvard.edu/china/

*The number of genera and species is based on Christenhusz and Byng 2016Christenhusz and Byng 2016:
Christenhusz MJM and Byng JW. 2016. The number of known plant species in the world and its annual increase. Phytotaxa 261 (3): 201ndash;217. https://doi.org/10.11646/phytotaxa.261.3.1, which may differ from the number of genera in GRIN-Global.