Herbs with a pungent watery juice, alternate leaves without stipules, and regular hypogynous flowers in racemes or corymbs. Pedicels without bractlets. Sepals 4, deciduous. Petals 4, forming a cross-shaped corolla. Stamens 6, two of them shorter. Fruit a silique or silicle. (See Chap. IV., Part I. for dissection of typical flower.) The genera are distinguished by the pods and seeds, the flowers in all cases being much alike. The seeds are exalbuminous, consisting entirely of the embryo, which is folded up in a variety of ways. The radicle may be bent so as to lie against the edge of the cotyledons, and the seed when cut through crosswise shows this section: ; The cotyledons are then said to be accumbent. Or the radicle may be folded against the back of the cotyledon, showing this cross-section:, In which case the cotyledons are said to be incumbent; and if, besides being incumbent, the cotyledons are doubled round the radicle, thus:, they are then conduplicate.
* Pod dehiscent by 2 valves, usually much longer than broad.
1. Nasturtium. Flowers white or yellow. Pod terete, oblong-linear or ellipsoid. Seeds in two rows in each cell, globular, without a wing. Cotyledons accumbent.
2. Barbare'a. Flowers yellow. Pod somewhat 4-sided, the valves strongly 1-nerved. Seeds in one row in each cell. Cotyledons accumbent.
3. Vesicaria. Flowers yellow. Plant densely hoary with stellate hairs. Pods ovate or globose. Seeds flattened, in two rows in each cell. Cotyledons accumbent.
4. Dentaria. Flowers white or pale purple. Pod lanceolate, flat.
Seeds wingless, on broad seed-stalks. Stem-leaves 2 or 3 in a whorl; stem naked below. Boot-stock toothed or tuberous. Cotyledons accumbent.
5. Cardam' ine. Flowers white or rose-coloured. Pod linear or lanceolate, flat, the valves nerveless. Seeds wingless, on slender seed-stalks. Stem leafy below. Cotyledons accumbent.
6. Ara'bis. Flowers white or whitish. Pod linear or elongated, flattened, the valves usually with a distinct mid-rib. Stem leafy. Cotyledons accumbent.
7. Erys'imum. Flowers yellow (or creamy). Pod linear, distinctly 4-sided. Stigma broadly 2-lobed. Pedicels of the pods diverging from the stem. Leaves simple, not clasping. Pubescent with appressed hairs. Cotyledons incumbent.
8. Sisym brium. Flowers yellow, small. Pods awl-shaped or 4-6sided, the valves 1-3-nerved. Stigma small. Cotyledons incumbent.
9. Hes'peris. Flowers large, purple. Pod terete, elongated. Stigmaiobes narrow, erect. Cotyledons incumbent.
10. Bras'sica. Flowers yellow. Pod linear or oblong, nearly terete, or 4-sided, with a distinct beak extending beyond the end of the valves. Seeds usually in one row. Cotyledons conduplicate.
11. Diplotax is. Sepals, petals, and stamens almost as in Brassica.
Pods slender, on slender spreading pedicels. Beak conical, usually short. Seeds in two rows.
* * Pod dehiscent by 2 valves, comparatively short. + Silicle compressed parallel with the broad partition or globular.
12. Draba. Flowers white. Pod flat; seeds several or many, 2 rows in each cell. Cotyledons accumbent. Low herbs.
13. Alys'sum. Flowers pale yellow or white. Pod orbicular, flat, 2-4-seeded.
14. Camel'ina. Flowers yellow. Pod pear-shaped, pointed; valves 1-nerved. Cotyledons incumbent.
15. Nes'lia. Flowers very much as in the last. Pod nearly globular hardly one-twelfth of an inch across, usually only 1-celled and 1-seeded, wrinkled, tipped with the slender style.
+ + Silicle compressed contrary to the narrow partition.
16. Capsel' la. Flowers white. Pod obcordate-triangular; valves boat-shaped, wingless. Seeds numerous. Cotyledons incumbent.
17. Thlas'pi. Flowerswhite. Pod obovate or obcordate,winged. Seeds several. Cotyledons accumbent.
18. Lepid'lum. Flowers white or whitish. Pod roundish, very flat; the valves boat-shaped and winged. Seeds solitary.
19. Seneble'ra. Flowers greenish-white, very small. Pod 2-seeded, the valves wrinkled and separating at maturity as 2 closed one-seeded nutlets. Prostrate diffuse herbs, with a disagreeable characteristic odour.
* * * Pod indehiscent, fleshy, jointed.
20. Caki'le. Flowers purplish. Pod 2-jointed, fleshy. Leaves fleshy.
21. Raph'anus. Flowers yellow, turning whitish or purplish. Pod elongated, several-seeded, mostly constricted between the seeds. Cotyledons conduplicate.
1. N. officinale, R. Br. - (Water-Cress.) Flowers white. Stem spreading and rooting. Leaves pinnate; leaflets 3-11, roundish or oblong, nearly entire. Pods oblong-linear. - Ditches and streamlets.
2. N. palus'tre, DC. (Marsh Cress.) Flowers yellow. Stem erect. Leaves pinnately parted, the lobes cut-toothed. Pods ovoid. - Wet places.
3. N. lacus'tre, Gray. (Lake Cress.) Flowers white. An aquatic plant, with the submerged leaves finely dissected; the leaves out of the water oblong, and either entire, serrate, or pinnatifid. Pods ovoid, 1-celled.
4. N. Armora'eia, Fries. (Horseradish.) Has escaped from gardens in many places. Flowers white. Root-leaves very large, oblong, and generally crenate; stem-leaves lanceolate. Pods globular. Roots very large.
5. N. trachycar'pum, Gray. Flowers white. Stem nearly glabrous, erect, branching. Leaves lyrate-pin-natifid. Pods oblong-linear, somewhat roughened, soon recurved, shorter than the awl-shaped style. - N. W., in beds of pools and streams.
6. N. amphib'ium, R. Br. Flowers white. Stem tall, erect, branching above, sparingly pubescent. Leaves lyrate-pinnatifid, rough-pubescent, the lobes coarsely toothed. Pods several times longer than the style, but much shorter than the pedicels. - Wet places.