Flora of North America species comparison

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Ruppia maritima

Ruppia

beak ditch-grass, ditch grass, ruppie maritime, sea ditch-grass, spiral ditch-grass, western ditch-grass, widgeon-grass, wigeongrass

ditch-grass, rruppia, widgeon grass, widgeonweed
Habit Herbs, rooting at proximal nodes.
Stems

to 50 cm × 0.1–0.7 mm.

Leaves

6–10.5 cm;

blade 0.3–0.5 mm, apex ± obtuse.

blade entire proximally, minutely serrulate distally, apex ± obtuse to acute;

veins 1.
Inflorescences

peduncles with 0–3[–4] coils, 0.5–16.5 × 0.5 mm.

fewer than 20-flowered, at first enclosed by sheathing leaf bases.
Flowers

pistils 4–8.

bisexual;

anthers 2-loculed, locules separated by broad connective;

stipe elongating after anthesis.
Fruits

1.8–2 × 0.7–1.5 mm;

gynophore 1.2–1.9 cm;

beak terminal, slightly recurved, 0.6–1 mm.

beaked, long-stipitate;

beak erect or slightly recurved.
2n

= 16.

Ruppia maritima

Ruppia
Phenology Flowering spring–fall.
Habitat Shallow waters of brackish streams, ditches, and lakes along ocean shore
Elevation 0–200 m (0–700 ft)
Distribution
from FNA
AK; AL; CA; CT; DE; FL; GA; LA; MA; MD; ME; MS; NC; NH; NJ; NY; OR; RI; SC; TX; VA; WA; BC; NB; NF; NS; ON; PE; QC; SK; SPM; Central America; South America; coastal Mexico; West Indies; Bermuda; Eurasia; Africa; Australia
[WildflowerSearch map]
[BONAP county map]
from USDA
Almost worldwide
[BONAP county map]
Discussion

No specimens have been seen from Washington, D. C., but the species is to be expected there.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Considerable confusion exists about North American taxa of Ruppia. Two distinct forms, along with several intermediates, are known: one with short peduncles with four or fewer spirals and another with long peduncles with five or more coils (often many more). Usually, those with few coils are in brackish waters near the coast, whereas those with many coils are inland, often in lakes that have high mineral contents. The forms have been considered variants variants of one species, R. maritima (M. L. Fernald and K. M. Wiegand 1914); more recently they have been accepted at species level (R. F. Thorne 1993). I am adopting Thorne’s concepts.

Species ca. 10 (2 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Peduncle with 5 or more coils in fruit, longer than 30 mm; plants mostly from inland localities
R. cirrhosa
1. Peduncle with fewer than 5 coils in fruit, shorter than 25 mm; plants mostly from coastal localities
R. maritima
Source FNA vol. 22. FNA vol. 22.
Parent taxa Ruppiaceae > Ruppia Ruppiaceae
Sibling taxa
R. cirrhosa
Subordinate taxa
R. cirrhosa, R. maritima
Synonyms R. maritima var. brevirostris, R. maritima var. exigua, R. maritima, R. maritima var. longipes, R. maritima var. obliqua, R. maritima var. rostrata, R. maritima var. subcapitata
Name authority Linnaeus: Sp. Pl. 1: 127. (1753) Linnaeus: Sp. Pl. 1: 127. 1753;, Gen. Pl. ed. 5; 61, (1754)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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