MUSTARD FAMILY. 51 



10. CRUCIFERffi, MUSTARD FAMILY. 



Herbs, with watery juice, of a pungent taste (as exemplified in 

 Horseradish, Mustard, Water-Cress, &c.), at once distinguished by 

 the cruciferous flower (of 4 sepals, 4 petals, their upper part gen- 

 erally spreading above the calyx in the form of a cross), the tetra- 

 dynamous stamens (i. e. 6, two of them shorter than the other four) ; 

 and the single 2-celled pistil with two parietal placenta?, forming the 

 kind of pod called a silique, or when short a silicle. (See Lessons, 

 p. 92, fig. 187, 188, for the flower, and p. 133, fig. 310, for the fruit.) 

 The embryo fills the whole seed, and has the radicle bent up agaii^t 

 the cotyledons. Flowers in racemes, which are at first short, like 

 simple corymbs, but lengthen in fruiting : no bracts below the pedi- 

 cels. The blossoms are all nearly alike throughout the family ; so 

 that the genera are mainly known by the fruit and seed, which are 

 usually to be had before all the flowers have passed. 



^ 1. Fruit a true pod, opening lengthwise by two valves, which fall aicay and leave 



the thin persistent partition when ripe. 

 * Seeds or ovules more than two in each cell. 



*-Pod benked or pointed beyond the summit of the valves, or the style with a conical 

 base. Seeds spherical, the cotyledons wrapped around the radicle. 



1. BRASSICA. Flowers yellow. Pods oblong or linear. 



-t- * Pod not beaked or conspicuously pointed, 

 ft- Neither flattened nor 4-sided, but the cross-section nearly circular. 



2. SISYMBRIUM. Pods in the common species shortish, lance-awl-shaped, close- 



pressed to tho stem. Seeds oval, marginless. Flowers small, yellowish. 



3. NASTURTIUM. Pods shortish or short (from oblong-linear to almost spherical). 



Seeds in 2 vows in each cell, globular, marginless. Flowers yellow or white. 



4. HESPKRIS. Pods long and slender, with a single row of marginless seeds in 



each cell (as broad as the partition); the radicle laid against the back of one 

 of the cotyledons. Flowers rather large, pink-purple. Stigma of 2 erect 

 blunt lobes. 



5. MALCOLMIA. Pods somewhat thickened at the base. Stigma of 2 pointed 



lobes. Otherwise as No. 4. 



6. MATTHIOLA. Pods long and narrow : seeds one-rowed in each cell (as broad 



as the partition), flat, wing-margined; the radicle laid against one edge of the 

 broad cotyledons. Flowers pink-purple, reddish, or varying to white, large 

 and showy. 



+-**-* Pod lonr/ and slender, linear, 4-sided (the cross section square or rhombic), or 

 if flattened hariny a strong salient midrib to the valves. Seeds maryinless, 

 mostly single-rowed in each cell. Flowers yellow or oranye, never white. 

 a. Lateral sepals sac-shaped at the base. 



7. CHEIRANTHUS. Seeds flat; the radicle laid against the edge of the broad 



cotyledons. Flowers showy. Leaves entire. 



b. Sepals nearly equal and alike at the base. 



8. ERYSIMUM. Seeds oblong; the radicle laid against the back of one of the 



narrow cotyledons. Leaves simple. 



9. BARBAREA. Seeds oval; the radicle laid against the edge of the broad 



cotyledons. Leaves lyrate or pinnatifid. . 

 2. SISYMBRIUM. Seeds oblong; the radicle laid against the back of one of the 



cotyledons. Flowers small. Leaves twice pinnatifid. 



HH. ** ++ Pod flattened parallel to the partition ; the valves flat or flattisli : so are the 

 seeds: radicle against the edge of the cotijledons. Flowers white or purple. 



10. ARABIS. Pod long and narrow-linear, not opening elastically ; the valves 



with a midrib. Seeds often winged or margined. 



11. CARDAMIXK. Pods linear or lanceolate; the valves with no or hardly any 



midrib, opening elastically from the base iipwards. Seeds marginless and 

 slender-stalked, one-rowed in each cell. No scaly-toothed rootstock. 



