MUSTARD PLANTS 365 



XX. CRUClFERiE. Mustard Family. 



Herbs, mostly of small stature, with alternate mostly simple leaves: 

 flowers 4-merous as to envelopes, the 4 petals usually standing 90 

 degrees apart and thereby forming a cross (whence the name Cruciferse, 

 or "cross-bearing"); stamens usually 6, 2 of them shorter: fruit 

 a silique or silicle. A very natural or well-marked family, with about 

 180 genera and nearly 2,000 species. Familiar plants are mustard, 

 shepherd's purse, honesty, cress, pepper-grass, wallflower, stock, 

 cabbage, turnip, radish, horse-radish. 



a. Fruit a silique (much longer than broad). 



b. Silique tipped with a long point or beak, extending 



beyond the valves, the latter more than 1-nerved. . 1. Brassica 

 bb. Silique not prominently beaked beyond the valves. 



c. Flowers yellow 2. Barbarea 



cc. Flowers white or purple. 



d. Valves with a midrib, or 6eeds in 2 rows. 



e. Stigma deeply 2-lobed: flowers large 3. Matthiola 



ee. Stigma but slightly, if at all 2-lobed 4. Arabis 



dd. Valves without midrib. 

 e. Seeds in 1 row. 



F. Stems leafless below, with 2 or 3 leaves near 



middle: rootstock scaly 5. Dcntaria 



ff. Stems leafy: roots more fibrous 6. Cardamine 



ee. Seeds in 2 rows in each cell.' (Water plants. 

 See Radicula.) 

 aa. Fruit a silicle (short and broad). 



b. Partition in the pod parallel to the sides. 



c. Fruit not much compressed: seeds minute, in 2 



rows in each cell 7. Radicula 



CC. Fruit quite flattened, 2-8-secded 8. Alyssum 



bb. Partition crosswise the pod. 



c. Pod obcordate, many-seeded '.». Capsi Ua 



cc. Pod orbicular, 2-seeded: corolla regular 10. Le iridium 



ccc. Pod rounded or ovate: corolla irregular with un- 

 equal petals 1 1 . I In ria 



aaa. Fruit fleshy, indehiscent, constricted between the 



seeds 12. Raphanua 



1. BRASSICA. Mustard. 



Erect branchy herbs, mostly annual, with more or less lyrate lower 

 leaves, and small yellow flowers in racemes or panicles: petals clawed or 

 narrowed below, the limbs spreading horizontally: silique narrow, cylindrical 

 or 4-angled, the valves 1-5-nerved and the seeds in 1 row in each locule. 

 Cabbage, cauliflower, and turnip also belong to this genus. The three fol- 

 lowing are common weeds introduced from Europe: 



