328 BRASSICACEAE 



29. L. dictyotum A. Gray. Annual; stems branched at the base, spread- 

 ing, 3-10 cm. long, hirsute; basal leaves either linear, entire, or pinnatifid with 

 distant linear lobes; stem-leaves narrowly linear; petals none or rudimentary; 

 stamens 4; pod ovate, wing-margined, with prominent acute lobes, hirsute, 3 

 mm. long. Sandy places: Wash. Ida. Utah Calif. Son. Mr-Je. 



4. THLASPI (Tourn.) L. PENNY CRESS, PENNY-GRASS. WILD SWEET 



ALYSSUM. 



Glabrous annuals or perennials, with undivided and often clasping leaves. 

 Flowers racemose, perfect. Sepals equal. Petals white, or rarely pink or 

 purplish, obovate or oblanceolate. Stamens free, unappendaged ; anthers short, 

 oval. Styles slender or none; stigma small, entire. Capsules orbicular, oblong 

 or cuneate; valves strongly keeled, often winged, especially towards the apex. 

 Seeds 2-8 in each cell. 



Pods orbicular in outline, broadly wing-margined and deeply notched at the apex ; sepals 



green; annuals. 1. T. arvense. 



Pods obovate or oblanceolate-cuneate in outline, with narrow margins, acute, truncate 

 or slightly notched at the apex; sepals with white or rarely purplish margins; 

 perennials. 



Petals 2.5-3 mm. long; pod oblanceolate-cuneate, 2-2.5 mm. wide. 2. T. parviflorum. 

 Petals 4-7 mm. long; pods cuneate or obovate-cuneate, 3 mm. or more wide. 



Pods acutish at the apex, neither emarginate nor retuse. 3. T. californicum. 



Pods rounded or truncate at the apex, emarginate or retuse. 

 Pods rounded at the apex; sinus narrow. 



Caudex rather slender; stem 1-2 dm. high; petals spatulate, about 5 mm. 



long. 4. T. Nuttallii. 



Caudex stout, densely cespitose; stem less than 1 dm. high; petals broadly 



obovate, 6-7 mm. long. 5. T. color adense. 



Pods truncate or nearly so at the apex; sinus very broad and open. 



Stem 2-3 dm. high; stem-leaves ample, broader than the basal ones; sepals 



green, with white margins. 6. T. glaucum. 



Stem 1 dm. or less; stem-leaves reduced; sepals and often also petals 

 purplish. 7. T. purpurascens. 



1. T. arvense L. Annual, glabrous; stem 1.5-4.5 dm. high; basal leaves 

 early deciduous, petioled; blades oblanceolate; stem-leaves oblong or elliptic, 

 dentate, the upper auricled and clasping at the base; petals about 4 mm. long, 

 oblanceolate or spatulate; pod 12-18 mm. long, 10-15 mm. broad. Waste places 

 and roadsides: Lab. -Fla. Colo. Utah B.C.; adv. or nat. from Eu. Plain 

 Submont. My-Jl. 



2. T. parviflorum A. Nels. Stems few, 1-3 dm. high; lower leaves rosulate 

 at the base, glabrous, 5-20 mm. long, short-petioled, elliptic or oval; stem-leaves 

 5-12 mm. long, oblong, sagittate and clasping at the base; petals oblanceolate; 

 pod 5-7 mm. long, scarcely winged, slightly emarginate. Open valleys: Wyo. 

 Mont. Submont. Mont. Je. 



3. T. californicum S. Wats. Stems 1-2 dm. high, simple; basal leaves 

 petioled, 1-3 cm. long, oval or spatulate; stem-leaves oval, 5-10 mm. long, sagit- 

 tate and clasping at the base; petals spatulate, 4-5 mm. long; pod cuneate, 5-7 

 mm. long. Mountain valleys: Mont. Utah Calif. Wash. Submont. Sub- 

 alp. Je-Au. 



4. T. Nuttallii Rydb. Stems solitary or few, 1-2 dm. high, leafy; basal 

 leaves petioled, 1-2 cm. long, glabrous, oval, spatulate, or obovate; stem-leaves 

 rounded-oval, about 1 cm. long, cordate and clasping at the base; pod cuneate- 

 obcordate, about 7 mm. long. Valleys and hillsides: Mont. Colo. Wash. 

 Submont. -Mont. My-Jl. 



5. T. coloradense Rydb. Stems 2-8 cm. long; basal leaves broadly spatu- 

 ate, 1-2 cm. long, fleshy, sinuately crenate or subentire; stem-leaves oblong or 

 obovate, 3-10 mm. long, obtuse; pod obovate, about 6 mm. long; wing-margins 

 very narrow. Alpine peaks: Colo. Utah. Alp. 'Mont. Jl-Au. 



6. T. glaucum A. Nels. Stems leafy, 1-3 dm. high; basal leaves peti- 

 oled, 2-3 cm. long, oval or obovate, glabrous and glaucous, entire or repand; 

 stem-leaves ovate-oblong, cordate and clasping at the base; petals about 6 mm. 

 long; pod cuneate, wing-margined above. Valleys: Mont. Colo. Utah. Sub- 

 mont. Subalp. Je-Jl. 



