BRASSICACEAE 483 



1. Leavenworthta aurea Torr. Foliage glabrous. Stems erect or decumbent, 

 4-15 cm. long, often branched at the base : leaves mainly basal, a few on the stems ; blades 

 divided into 5-9 angular-toothed segments, the terminal one largest : pedicels 1-4 cm. 

 long, ascending, often curved : sepals oblong, 3.5-4 mm. long, obtuse : petals yellow, or 

 purplish with a yellow base, twice as long as the sepals, narrowly cuneate, retuse at the 

 apex: pods linear-oblong, not torulose, 1.5-2 cm. long, each tipped with a slender style 

 1-2 mm. long : seeds 4-14 : cotyledons orbicular, cordate ; radicle straight. 



On rocks, Arkansas to Tennessee, south to Alabama and Texas. 



2. Leavenworthia tmiflora (Michx.) Britton. Foliage glabrous or nearly so. 

 Stems 2-15 cm. long, erect or ascending, simple or sparingly branched : leaves mainly 

 basal, 2-10 cm. long ; blades divided into 5-17 unequal toothed or angular segments, the 

 terminal one Jlarger than the rest : pedicels 2-15 cm. long, erect or ascending : sepals 

 oblong, obtuse : petals white or purplish, with a yellow base, cuneate-oblanceolate, retuse at 

 the apex : pods linear-oblong, 2.5-3.5 cm. long, each tipped with a stout style 1 mm. 

 long: seeds 4-18 : cotyledons oval ; radicle oblique. [L. Michauxii Torr. ] 



In dry soil, Indiana to Missouri, Tennessee and Alabama. 



3. Leavenworthia stylosa A. Gray. Foliage glabrous. Stems 2-12 cm. long, as- 

 cending or prostrate : leaves mainly basal, 2-8 cm. long ; blades divided into 3-7 entire or 

 angular segments, the terminal one much larger than the rest : pedicels ascending, 4-10 

 cm. long : sepals oblong, about 5 mm. long, obtuse : petals yellow, emarginate, about twice 

 as long as the sepals : pods oblong, 4-8 mm. long, each tipped with a slender style 4-6 

 mm. long, not torulose : seeds 6-8 : cotyledons oval ; radicle oblique. 



In cedar woods, Tennessee. 



4. Leavenworthia torulosa A. Gray. Foliage glabrous. Stems 2-15 cm. long, 

 erect or ascending, sometimes almost wanting : leaves mainly basal, 2-10 cm. long ; blades 

 pinnately-divided into entire angled or lobed segments, sometimes represented by a large 

 terminal segment and two small lateral ones : pedicels erect or ascending, 4-10 cm. long : 

 sepals narrowly oblong, 5 mm. long, obtuse : petals purplish, with a yellow base, nearly 

 twice as long as the sepals, emarginate : pods linear, 2-3 cm. long, conspicuously con- 

 stricted below between the seeds, each tipped with a slender style 2-3 mm. long : seeds. 

 4-14 : cotyledons oval ; radicle oblique. 



In wet soil, cedar barrens, Kentucky and Tennessee. 



23. ARABIS L. 



Annual or perennial herbs, with glabrous or glaucous foliage, or pubescent with fork- 

 ing or stellate, or rarely simple hairs. Leaves alternate, sometimes mainly basal : blades 

 entire, toothed or pinnatifid. Flowers perfect, in terminal or axillary racemes. Sepals 

 4, equal or nearly so, sometimes saccate at the base. Corolla white, pink, purple or yellow- 

 ish : petals 4, entire or emarginate, often with claws. Stamens 6 : filaments free, unap. 

 pendaged. Ovary sessile : stigma capitate or 2-lobed. Ovules numerous. Pods elongated, 

 flat, the valves sometimes nerved or keeled, not dehiscent. Seeds in 1 row in each cavity, 

 marginless, margined or winged. Cotyledons accumbent or incumbent. ROCK CRESS. 



Basal leaves with pinnatifid blades. 

 Sepals 1-2 mm. long : seeds winged. 



Pods 2-2.5 cm. long, the valves obscurely nerved>t the base: seeds narrowly winged. 



1. A. Virginica. 



Pods 5-7.5 cm. long, the valves nerved below the middle: seeds broadly winged. 2. A. petiolaris. 

 Sepals 2-2.5 mm. long : seeds wingless. 3. A. lyrata. 



Basal leaves with toothed blades. 



Seeds wingless. 4. A. dentata. 



Seeds winged or margined. 



Capsules erect or nearly so, sometimes appressed. 



Corollas over 7 mm. broad : capsules not appressed : style 1 mm. long. 5. A. patens. 



Corollas less than 7 mm. broad : capsules appressed : stigma sessile. 6. A. hirsuta. 



Capsules recurved. 



Plants glabrous, glaucous : pods 1-2 mm. wide. 7. A. laevigata. 



Plants pubescent, at least below : pods 2.5-3.5 mm. wide. 8. A. Canadensis* 



1. Arabia Virginica ( L. ) Trelease. Annual or biennial, sparingly hirsute or nearly 

 glabrous. Stems usually branched at the base, the branches ascending or decumbent, 1-4 

 dm. long, simple or branched : basal and stem-leaves quite similar, 2-7 cm. long ; petioles 

 much shorter than the blades, margined ; blades deeply pinnatifid into uniform entire or 

 1-2- toothed nearly oblong or linear segments : pedicels finally spreading or ascending, 

 3-6 mm. long : sepals narrowly oblong, 1 mm. long, obtuse : petals white : pods linear, 

 2-2.5 cm. long, straight, ascending or somewhat spreading: seeds in 1 row, winged.. 

 [A. Ludoviciana (Hook.) C. A. Meyer.] 



In sandy or rocky soil, Virginia to Missouri, Florida and Texas. Spring. 



