62 CRUCIFER^. (mustard FAMILY.) 



ing a cross. Stamens 6, two of them inserted lower down and shorter 

 (rarely only 4 or 2). Pod usually 2-celled by a thin partition stretched 

 between the two marginal placentae, from which when ripe the valves 

 separate, either much longer than broad (a silique), or short (a silicle), 

 sometimes indehiscent and nut-like (nucumentaceous), or separating across 

 into 1-seeded joints (lomentaceoiis). Seeds campylotropous, without albu- 

 men, filled by the large embryo, which is curved or folded in various 

 ways : i. e. the cotyledons decumbent, viz., their margins on one side applied 

 to the radicle, so that the cross-section of the seed appears thus o= ; or 

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

 thus o||. 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 Leavenwortliia 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. (The characters of the 

 genera are taken almost wholly from the pods and seeds ; the flowers 

 being nearly alike in all.) 



SERIES I. Pod 2-celled, regularly dehiscent by 2 valves. 



* Pod comiiressed parallel to the broad partition. Seeds flat or flattisli, orbicular or oval ; 



cotyledons accumbent or nearly so. 

 -•- Pod large, oblong-elliptical , valves nerveless. Seeds in 2 rows. Flowers yellow. 



1 . Selenia. Leaves pinnatisect. Raceme leafy-bracteate. Seeds winged. 



-»- -•- Pod linear; valves nerveless. Seeds in one row. Flowers yellow only in n. 2. 



2. L,eavenworthia. Seed winged ; embrj^o straight or nearly so. Annual ; stem often 



scapose, 1 - few-flowered. 



3. Dentaria. Stem naked below, 2-3-leaved. Pod coriaceous, with thick placentas, 



long-styled. Seeds wingless ; cotyledons thick, very unequal. 



4. Cardaixiine. Stem leafy. Pod coriaceous, with thick placentas. Seeds wingless; 



cotyledons flattened, cfjual. 



I- -I- -(- Pod linear, or oblong, or orbicular; valves l-nerved or nerveless. Seeds in 2 rows 

 (except in species of n. 5). 



6. Arabis. Pod long-linear, the flat or flattish valves more or less l-nerved. Seeds 

 winged or wingless. Flowers white to purple. Stems leafy, at least below. 



6. Draba. Pod oval to narrowly oblong or lanceolate ; valves flat or flattish, faintly 



nerved or veined. Seeds wingless, numerous. 



7. Alyssiim. Pod orbicular : valves veinless, somewhat convex with flattened margin. 



Seeds wingless, 2-4. 



♦ * Pod terete or turgid, or 4-angled by the prominent midnerves. Seeds wingless, more or 



less turgid. 



■t- Pods short. (See also n. 11.) 



8. Ijesquerella. Pod globular-inflated, about 4-seeded ; valves ner\-eless. Cotjdedons 



accumbent. Flowers yellow. 



9. Camelina. Pod obovoid, many-seeded, valves l-nerved; style slender. Cotyledons 



incumbent. Flowers yellow. 

 10 Subularia. Pod ovoid or globular, few-seeded , valves l-nerved ; style none. Coty- 

 ledons long, folded transversely. Flowers white. Dwarf stem less aquatic. 



