CRUCLFER^E. (MUSTARD FAMILY.) 15 



ORDER 6. CRUCIFER.E. (MUSTARD FAMILY.) 



Herbs, with a pungent watery juice, cruciform corolla, tetradynamous 

 stamens, and a 2-celled pod with 2 parietal placentae. Sepals 4, decid- 

 uous. Petals 4. Ovary 2-celled by a partition which stretches across 

 from the placentae, rarely 1 -celled. Style undivided or none ; stigma 

 entire or 2-lobed. Fruit a silique or silicle, the two valves falling away 

 from the partition, which persists and is called the replum, in a few 

 genera indehisceut. Ovules few or numerous. Flowers generally in 

 racemes and without bractlets. Leaves alternate, without stipules. 

 The mature pods are necessary for analysis. 



I. Pod dehiscent, 2-valved. 

 * Pod strongly compressed parallel with the broad partition : cotyledons accumbent (i. e. 



the radicle and cotyledons appearing in cross-section thus 08)- 

 - Pod short ; valves nerveless or faintly 1-nerved : flowers white or yellow. 

 1. Draba. Pod ovate to oblong or linear, few to many-seeded; valves flat or convex. 

 Seeds wingless. Low, flowers racemose. 



)- -t- Pod elongated. 



Valves nerveless ; replum thickened ; seeds wingless : flowers white : leaves all petioled. 

 2 Cartlainine. Pod moderately beaked or pointed. Stems leafy, with elongated 



racemes. 



H- -H- Valves 1-nerved ; replum thin ; seeds flat, often winged or margined : flowers white to 

 purple (sometimes yellowish in Streptanthas) : canline leaves (if any) sessile. 



3. Parrya. Anthers linear. Petals broadly obovate. Seeds in one or two rows. Scape 



naked. 



4. Arabis. An there short, scarcely emarginate at base. Petals with a flat blade and 



claw. Calyx short or narrow, rarely colored. Seeds in 1 or 2 rows. 



5. Streptantlius. Anthers elongated, sagittate at base. Petals often without a dilated 



blade, more or less twisted or undulate, the claw channelled. Calyx dilated and 

 usually colored. Seeds in one row. 



* * Pod terete or 4-angled, slightly or not at all compressed ; seeds not margined. 

 - Pod long-linear (1 to 4 inches) ; valves 1-nerved; seeds in ] row, oblong, somewhat flat- 

 tened, cotyledons incumbent (i. e. the radicle and cotyledons appearing in cross- 

 section thus oZ>). Stout biennials or perennials. 



H- Flowers greenish-yellow to purple : anthers sagittate. 



6. Caulantlms. Petals with abroad claw, somewhat dilated above and undulate, little 



longer than the broad sepals, greenish-yellow or purple. Filaments included. Stigma 

 nearly sessile, somewhat 2-lobed. Pod sessile, 3 inches long or more. 



7. Thclyportium. Petals with narrow claw and flat linear to rounded limb, much ex- 



ceeding the narrow sepals, usually pink to purple. Filaments often exserted. Style 

 short ; stigma mostly entire. Pod sessile or short-stipitate. 

 H- -* Flowers yellow. 



8. Stanley a. Pod somowhat terete, long-stipitate. Stigma sessile, entire. Anthers not 



sagittate, spirally coiled. Leaves entire or pinnatifid. 



9. ICrysimum. Pod 4-angled, sessile. Stigma 2-lobed. Anthers sagittate, not coiled. 



Leaves narrow, entire or repandly toothed. 



- *- Pod linear, mostly less than 1 inch long ; valves 1 to 3-nerved ; seeds in 1 or 2 rows, 

 globose to oblong : flowers usually yellow (white or pinkish in Smeloivslcia) : at least 

 the lower leaves pinuatifid. 1 



1 Lrassica, an introduced genus, may be looked for in this group, differing from the other 

 genera in its nearly terete pod with a long stout beak, globose seeds with the cotyledons 

 infolding the radicle, and long sagittate anthers. See foot-note, p. 23. 



