London J. Bot. 4: 77, plate 5. 1845.

Common names: Spectacle-pod
Etymology: Greek di- , two or double, and thyreos, shield, alluding to spectacle-shaped fruits
Treatment appears in FNA Volume 7. Treatment on page 607. Mentioned on page 237, 240, 571.

Annuals or perennials; (rhizomatous); not scapose; densely pubescent, trichomes stalked, stellate to subdendritic, sometimes as simple clavate papillae on fruits. Stems erect or decumbent, branched basally and distally. Leaves basal and cauline; petiolate or subsessile; basal rosulate, petiolate, blade margins dentate, sometimes repand, rarely pinnatifid; cauline petiolate, sessile, or subsessile, blade margins entire, dentate, or repand. Racemes (densely corymbose), considerably elongated or not elongated in fruit. Fruiting pedicels divaricate, stout, (straight, with 2 well-developed glands basally). Flowers: sepals erect, linear or oblong-linear, (forming tube, connivent), lateral pair saccate basally; petals (erect), white, lavender, or purplish, lingulate, (longer than sepals), claw undifferentiated from blade; stamens (erect), tetradynamous; filaments not dilated basally, (filiform); anthers narrowly linear or sagittate; nectar glands: lateral annular, median confluent with lateral; (gynophore to 0.5 mm). Fruits silicles, sessile or shortly stipitate, didymous, not winged, strongly angustiseptate; valves 1-seeded, ovate, suborbicular, or slightly broader than long, keeled, enclosing seeds when falling off, indurated around margin, (rim raised), pubescent (with branched or clavate, simple papillae); replum concealed by valve margin; septum complete; ovules 2 per ovary; style distinct, (pubescent); stigma capitate, entire. Seeds aseriate, flattened, not winged, oblong; seed coat (smooth), not mucilaginous when wetted; cotyledons accumbent. x = 10.


sw United States, nw Mexico.


Species 2 (2 in the flora).


1 Annuals; racemes elongated in fruit; fruit valves 3.5-5(-6) × 4-6(-7) mm, trichomes as simple, clavate papillae (stellate hairs absent or, rarely, restricted to fruit margins). Dithyrea californica
1 Perennials; racemes not elongated in fruit; fruit valves 8-11 × 8-10 mm, trichomes sessile, stellate, sometimes mixed with forked or, rarely, simple ones (clavate papillae absent). Dithyrea maritima