OregonFlora: Lepidium didymum vs. Brassicaceae

	Lepidium didymum	Brassicaceae
	lesser swinecress, lesser wartcress	mustard family
Habit	Plants annual, fetid, glabrous or pilose.	Herbs, rarely woody subshrubs or shrubs annual, biennial, or perennial; taprooted or with caudices, sometimes rhizomatous; trichomes unicellular, simple, 2–many-rayed, stellate, dendritic, or malpighiaceous; stalked or sessile; multicellular glands with uniseriate or multiseriate stalks present or absent.
Stems	often decumbent, 1–4.5(7) dm.	leafy or leafless, sometimes absent.
Leaves		basal and/or cauline; simple or compound; margins entire or variously divided, petiolate or sessile; without stipules.
Basal leaves	not rosulate, 1–6(8) cm, 1- or 2-pinnatisect; lobes entire or dentate, sometimes deeply lobed; petioles 0.5–4(6) cm.
Cauline leaves	similar to basal, 1.5–3.5(4.5) × 0.5–1.2 cm, bases not auriculate, petiolate to subsessile.
Inflorescences	rachises glabrous or pubescent with straight cylindrical trichomes, fruiting pedicels divaricate to horizontal; terete; straight or slightly recurved, 1.4–2.5(4) mm, glabrous or sparsely pubescent adaxially.	racemes; corymbs, or panicles, sometimes flowers solitary from a basal rosette.
Flowers	sepals caducous, 0.5–0.7(0.9) mm; petals elliptic to linear, 0.4–0.5 × ~0.1 mm, white; stamens 2; median; styles absent or obsolete, included in apical notch.	bisexual, hypogynous, radially or rarely bilaterally symmetric; sepals 4; in 2 decussate pairs, usually free; petals 4, forming a cross, rarely absent; stamens (2 or 4)6; in 2 whorls, tetradynamous, rarely equal in length or in 3 pairs of unequal length; median filaments free or rarely united; anthers dithecal, dehiscing by longitudinal slits; pollen 3(10)-colpate, trinucleate; pistils 1, 2-carpelled; ovaries superior; placentation parietal or rarely apical; septa complete, perforated, or lacking; styles 1; stigmas entire or 2-lobed, nectar glands receptacular.
Fruits	indehiscent, didymous, 1.3–1.7 × 2–2.5 mm; apical notch 0.2–0.4 mm deep; valves thick, rugose, glabrous, strongly veined; wingless.	typically 2-valved capsules (siliques or silicles), dehiscent or indehiscent; terete, 4-angled, flattened parallel to or perpendicular to septum; replums rounded or rarely winged.
Seeds	ovate, 1–1.2 × 0.7–0.8 mm; cotyledons incumbent.	uniseriately or biseriately arranged in each locule, rarely aseriate, mucilaginous or not when wetted, winged or wingless; cotyledons incumbent or accumbent, conduplicate.
2n	=32.

	Lepidium didymum	Brassicaceae
Distribution	[WildflowerSearch map] [BONAP county map]	[BONAP county map]
Discussion	Disturbed areas, fields, pastures. Flowering May–Oct. 0–300 m. Est, WV. CA, WA; north to British Columbia, eastern Canada and US, southern US; nearly worldwide. Exotic.	Cosmopolitan. 340 genera; 59 genera treated in Flora. This family includes many economically important crop plants that are grown as vegetables, sources of vegetable oils (canola), or condiments (table mustard, horseradish, wasabi), or ornamentals. It also includes some 130 species of weeds, including Arabidopsis thaliana, a model organism in experimental and molecular biology. The limits of Brassicaceae (Cruciferae) have not changed in the past two centuries because of characteristic floral and fruit morphology. Generic delimitation within the family is often difficult because of the reliance on fruit characters to separate genera. The ovule number per ovary is a taxonomically important character, which can easily be determined by counting the number of seeds and aborted ovules in the mature fruit. The use of seed number alone may be taxonomically unreliable because many ovules fail to develop into seeds, especially late in the season due to the lack of sufficient pollen.
Source	Flora of Oregon, volume 2, page 494 Ihsan Al-Shehbaz	Flora of Oregon, volume 2, page 434
Sibling taxa	L. acutidens, L. appelianum, L. campestre, L. chalepense, L. davisii, L. densiflorum, L. dictyotum, L. draba, L. graminifolium, L. heterophyllum, L. latifolium, L. montanum, L. nitidum, L. oblongum, L. perfoliatum, L. pinnatifidum, L. ruderale, L. sativum, L. strictum, L. virginicum
Synonyms	Coronopus didymus
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: OR Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Brassicaceae

lesser swinecress, lesser wartcress

mustard family

Habit

Plants annual, fetid, glabrous or pilose.

Herbs, rarely woody subshrubs or shrubs annual, biennial, or perennial; taprooted or with caudices, sometimes rhizomatous; trichomes unicellular, simple, 2–many-rayed, stellate, dendritic, or malpighiaceous; stalked or sessile; multicellular glands with uniseriate or multiseriate stalks present or absent.

Stems

often decumbent, 1–4.5(7) dm.

leafy or leafless, sometimes absent.

Leaves

basal and/or cauline; simple or compound;

margins entire or variously divided, petiolate or sessile; without stipules.

Basal leaves

not rosulate, 1–6(8) cm, 1- or 2-pinnatisect;

lobes entire or dentate, sometimes deeply lobed;

petioles 0.5–4(6) cm.

Cauline leaves

similar to basal, 1.5–3.5(4.5) × 0.5–1.2 cm, bases not auriculate, petiolate to subsessile.

Inflorescences

rachises glabrous or pubescent with straight cylindrical trichomes, fruiting pedicels divaricate to horizontal; terete; straight or slightly recurved, 1.4–2.5(4) mm, glabrous or sparsely pubescent adaxially.

racemes; corymbs, or panicles, sometimes flowers solitary from a basal rosette.

Flowers

sepals caducous, 0.5–0.7(0.9) mm;

petals elliptic to linear, 0.4–0.5 × ~0.1 mm, white;

stamens 2; median;

styles absent or obsolete, included in apical notch.

bisexual, hypogynous, radially or rarely bilaterally symmetric;

sepals 4; in 2 decussate pairs, usually free;

petals 4, forming a cross, rarely absent;

stamens (2 or 4)6; in 2 whorls, tetradynamous, rarely equal in length or in 3 pairs of unequal length;

median filaments free or rarely united;

anthers dithecal, dehiscing by longitudinal slits;

pollen 3(10)-colpate, trinucleate;

pistils 1, 2-carpelled;

ovaries superior;

placentation parietal or rarely apical;

septa complete, perforated, or lacking;

styles 1;

stigmas entire or 2-lobed, nectar glands receptacular.

Fruits

indehiscent, didymous, 1.3–1.7 × 2–2.5 mm; apical notch 0.2–0.4 mm deep;

valves thick, rugose, glabrous, strongly veined; wingless.

typically 2-valved capsules (siliques or silicles), dehiscent or indehiscent; terete, 4-angled, flattened parallel to or perpendicular to septum; replums rounded or rarely winged.

Seeds

ovate, 1–1.2 × 0.7–0.8 mm;

cotyledons incumbent.

uniseriately or biseriately arranged in each locule, rarely aseriate, mucilaginous or not when wetted, winged or wingless;

cotyledons incumbent or accumbent, conduplicate.

=32.

Lepidium didymum

Brassicaceae

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas, fields, pastures. Flowering May–Oct. 0–300 m. Est, WV. CA, WA; north to British Columbia, eastern Canada and US, southern US; nearly worldwide. Exotic.

Cosmopolitan. 340 genera; 59 genera treated in Flora.

This family includes many economically important crop plants that are grown as vegetables, sources of vegetable oils (canola), or condiments (table mustard, horseradish, wasabi), or ornamentals. It also includes some 130 species of weeds, including Arabidopsis thaliana, a model organism in experimental and molecular biology. The limits of Brassicaceae (Cruciferae) have not changed in the past two centuries because of characteristic floral and fruit morphology. Generic delimitation within the family is often difficult because of the reliance on fruit characters to separate genera. The ovule number per ovary is a taxonomically important character, which can easily be determined by counting the number of seeds and aborted ovules in the mature fruit. The use of seed number alone may be taxonomically unreliable because many ovules fail to develop into seeds, especially late in the season due to the lack of sufficient pollen.

Source

Flora of Oregon, volume 2, page 494
Ihsan Al-Shehbaz

Flora of Oregon, volume 2, page 434

Sibling taxa