CRUCIFERAE. 443 



Family 2. CRUCfpERAE B. Juss. 

 Mustard Family. 



Herbs, rarely somewhat woody, with watery acrid sap, alternate 

 leaves, and racemose or corymbose flowers. Sepals 4, deciduous, or 

 rarely persistent, the 2 outer narrow, the inner similar, or concave, or 

 saccate at the base. Petals 4, hypogynous, cruciate, nearly equal, gen- 

 erally clawed. Stamens 6, hypogynous, tetradynamous, rarely fewer. 

 Pistil i, compound, consisting of 2 united carpels, the parietal placentae 

 united by a dissepiment; style generally persistent, sometimes none; 

 stigma discoid or usually more or less 2-lobed. Fruit a silique or silicic, 

 generally 2-celled, rarely i -celled, in a few genera indehiscent. Seeds 

 attached to both sides of the septum ; endosperm none ; cotyledons 

 incumbent, accumbent or conduplicate. About 185 genera and 1500 

 species, of wide geographic distribution. 



The following wholly artificial key is designed to apply only to the species and genera 

 of our Flora. The natural alliances of the genera are largely based on minute charac- 

 ters. The family is also known as BRASSICACEAE. 



* Pod a silique or silicic, dehiscent into two valves to the base. 



f Pod an elongated-linear silique, or at least twice as long as wide. (See also 

 species of No. 29.) 



1. Silique borne on a long stipe. i. Stanleya. 



2. Silique terete, 4-sided, or compressed, very short-stipitate, or sessile on the receptacle. 



a. Silique tipped with the short slender style, or style none. 



Seeds globose or oblong, wingless. 



Seeds in 2 rows in each cell of the pod. 



Pubescence, when present, of simple hairs. 17. Roripa. 



Pubescence of forked hairs ; leaves finely dissected. 



30. Sophia. 

 Seeds in only i row in each cell. 



Leaves auricled at the base; flowers violet. 17. lodanthus. 



Leaves reniform or cordate, undulate or repand ; flowers white. 



8. Alliaria. 

 Leaves dentate or pinnatifid ; hairs simple ; flowers yellow. 



9. Sisymbrium. 

 Leaves finely dissected ; pubescence of forked hairs ; flowers yellow. 



31. Sophia. 

 Leaves entire, or slightly toothed. 



Stigma nearly entire, discoid ; plant glabrous. 2. l^helypodium. 

 Stigma 2-lobed ; plants more or less pubescent. 

 Flowers white or pink. 



Valves of the silique nerved. 



Leaves dentate to pinnatifid. 9. Sisymbrium. 



Leaves entire, cordate. 39. Conringia. 



Valves of the silique nerveless, rounded. 



32. Stenophragma. 



Flowers yellow. 34. Erysimum. 



Flowers large, purple, purplish or white. 38. Hesperis. 



Seeds flat, wingless or winged. 



Siliques 4-angled, the valves keeled; flowers yellow. 16. Barbarea. 

 Siliques flat or flattish. 



Valves of the silique nerveless. 



Seeds winged ; stem scape-like ; flowers few. 23. Leavenworthia* 

 Seeds wingless : valves of the silique elastically dehiscent. 



Stems leafy below or throughout. 19. Cardamine. 



Stems leafless below, 2-4-leaved above. 20. Dentaria. 

 Valves of the silique i-nerved or veiny, not elastically dehiscent. 



33. Arabis. 



b. Silique produced into a beak beyond the valves. 



Beak conic, very short in no. 13. 



Silique terete ; seeds in i row. 13. Brassica. 



Silique flat : seeds in 2 rows. 14. Diplotaxis. 



Beak flat, sword-shaped. 12. Sinapis. 



