CRUCIFER^E. (MUSTARD FAMILY.; 63 



or else incumbent, viz. the back of one cotyledon applied to the radicle, 

 thus oQ}. In these cases the cotyledons are plane; but they may be 

 folded upon themselves and round the radicle, as in Mustard, where they 

 are conduplicate, thus o^;. In Leavenworthia alone the whole embryo is 

 straight. — Leaves alternate, no stipules. Flowers in terminal racemes 

 or corymbs : pedicels rarely bracted. — A large and very natural family, 

 of pungent or acrid, but not poisonous plants. (Characters of genera 

 taken from the pods and seeds ; the flowers being nearly alike in all.) 

 I. SLLIQUOSiE. Pod long, a silique, opening by valves. 



Tribe I. ARABIDEiE. Pod elongated (except in Nasturtium). Seeds orbicular or 



oval, more or less flattened. Cotyledons accumbent, plane. 



* Seeds small and turgid, seldom half the breadth of the turgid pod. 



1. Nasturtium. Pod terete, linear, oblong or even globular. Flowers white or yellow. 



* * Seeds flat or flattish, scarcely narrower than the partition, except in some of No. 5. 



2. Leaven worthia. Pod oblong, flat; the valves nerveless. Seeds winged: embryo 



straight ! Flowers white or purplish, with a yellowish base. Leaves all radical. 



3. Dentaria. Pod flat, lanceolate ; the valves nerveless, opening elastically from the base. 



Seeds wingless, on broad seedstalks. Flowers white or purple. Stem naked below. 



4. Cardamine. Pod flat, linear or lanceolate 5 the valves nerveless, opening elastically. 



Seeds wingless, on slender stalks. Flowers white or purple. Stem leafy, at least below. 



5. Arabis. Pod linear, elongated, flat or flattish, rarely almost terete ; the valves commonly 



with a prominent midrib, or veiny, not opening elastically. Flowers white, whitish, or 

 purple. Stems leafy, at least below. 



6. Barbarea. Pod linear, more or less 4-sided, the rigid valves being keeled by a promL 



nent midrib. S3eds wingless. Flowers yellow. 



Tribe II. SISYMBRIE.3E. Pod elongated. Seeds thickish, mostly oblong. Cotyle 

 dons incumbent, narrow, plane. 



7. Erysimum. Pod sharply 4-angled, linear. Flowers yellow. 



8. Sisymbrium. Pods terete, 4- 6-angled, or flattish. Flowers white or yellow. 



Tribe III. BRASSICEJE. Pod linear or oblong. Seeds globular. Cotyledons in- 

 cumbent and conduplicate, folded round the radicle. 



9. Brassica (including Sinapis). Pod beaked or pointed beyond the end of the valves, 



or tipped with a rigid style, nearly terete, or 4-sided. Flowers yellow or whitish. 



II. SILICULOSiE. Pod short, a silicle or pouch, opening by valves. 



Tribe IV. ALYSSINEjE. Pod oval or oblong, flattened parallel to the broad parti- 

 tion, or globular. Cotyledons accumbent, plane 

 1. Nasturtium. Pod terete or globular with many small seeds. 



10. Draba. Pod flat, oval, oblong, or even linear, many-seeded. 



11. Alyssum. Pod flat, orbicular, 2- 4-seeded. 



12. Vesicaria. Pod globular-inflated, 4 -several -seeded. 



Tribe V. CAMELiINEJE. Pod turgid or somewhat flattened parallel with the broad 

 partition. Cotyledons incumbent, narrow. 



13. Camelina. Pod pear-shaped, many-seeded : style slender. Flowers yellow. 



14. Subularia. Pod globular, few-seeded : style none. Flowers white. 



Tribe VI. IjEPIDINE^ and THLASPIDEJE. Pod short; the boat-shaped 

 valves conduplicate or much flattened contrary to the narrow partition. Flowers white. 



15. Capsella. Pod many-seeded, obcordate-triangular, wingless. Cotyledons incumbent. 



16. Tiilaspi. Pod several-seeded, obovate or obcordate, winged. Cotyledons accumbent. 



17. Lepidium. Pod 2-seeded, flat, scale-shaped. Cotyledons incumbent or accumbent. 



18. Senebiera. Pod 2-seeded, didymous ; the valves rugose, separating at maturity from 



the little partition as two closed one-seeded nutlets. Cotyledons incumbent, narrow. 



