330 BRASSICACE.\E 



broadly spatiilate; fruit 11-12 mm. long and about 1 mm. wide, tapering at both 

 ends. High mountains: Colo. — -Utah — -Alta. Alp. — Subalp. 



8. DITHYREA Harv. 



Stellate caulescent annuals or perennials. Flowers perfect, racemose. Sep- 

 als ovate or oblong, erect or spreading, pubescent. Petals broadly spatulate, 

 with slender claws, white or purplish. Stamens 6, free and unappendaged; 

 anthers sagittate, linear. Pods didymous, strongly obcompressed ; cells sub- 

 orbicular. Stigma sessile, large, simple. Cotyledons accumbent. 



1. D. Wislizeni Engelm. Perennial oi» biennial with a taproot; stems 

 cinereous-stellate, 3-6 dm. high; leaves numerous, lanceolate, sinuately dentate, 

 cinereous-stellate, 3-6 cm. long; petals light yellow, 6 mm. long, long-clawed; 

 pedicels in fruit divaricate; cells of the fruit obliquely obovate, flat, margined, 

 about 5 mm. wide. Arid regions: Tex.— Ariz. — Utah. Son. 



8. PHYSARIA A. Gray. Double Bladder-pod. 



Stellate, cespitose perennials with taproots. Flowers perfect, racemose. 

 Sepals oblong, erect or ascending, equal at the base. Petals spatulate, yellow. 

 Stamens 6; anthers sagittate, linear. Fruit more or less distinctly didjanous, 

 inflated or obcompressed. Stjdes slender. Cotyledons accumbent. 



Cells of the pods much Inflated, the upper sinus acute, narrow. 



Pods deeply cordate at the base; lower sinus almost as deep as the upper. 



Pubescence short and close. 1. P. didymocarpa . 



Pubescence long and loose. 2. P. lanata. 



Pods not cordate at the base or slightly so; lower sinus none or very shallow. 

 Cells of the pods 5-10 mm. in diameter, without ridges on the sides. 

 Some of the basal leaves more or less flddle-shaped. 



Leaves of the decumbent flowering stems reduced; terminal lobe of the 

 basal leaves rounded or reniform, very obtuse, entire. 



3. P. ritulifera. 

 Leaves of the ascending flowering stems ample; terminal lobes of the basal 



leaves rhombic or ovate, acute or sometime obtuse, sinuate. 



4. P. floribunda. 

 None of the basal leaves flddle-shaped . 



Basal leaves oblanceolate or spatulate, acute, 2-4 cm. long; pods slightlj' 



cordate at the base. 5. P. acutifolia. 



Basal leaves rounded-obovate, 4-10 cm. long; pod acutish at the base. 



6. P. brassicoides. 

 Cells of the pods 10-18 mm. in diameter when fully developed, ridged on the sides. 



7. P. Newberrtji. 

 Cells of the pods not much inflated, the upper sinus shallow, open. 8. P. Geyeri. 



1. P. didymocarpa (Hook.) A. Gray. Stems nmuerous, 3-15 cm. long, de- 

 cumbent to erect; basal leaves 1-8 cm. long, with margined petioles and broadly 

 obovate, entire or sinuately toothed blades, finely and closely stellate; petals 

 8-14 mm. long, spatulate; pod 7-15 mm. in diameter. P. macrantha Blankin- 

 ship. Sandy or rocky hills and plains: Sask. — Colo. — -Utah — -Alta. Plain — 

 Mont. My-Jl. 



2. P. lanata (A. Nels.) Rydb. Stems erect or ascending, 1-2 dm. high; 

 basal leaves numerous, 4-8 cm. long; blades broadly obovate to flabelliform- 

 spatulate, sinuate-dentate; petals about 8 mm. long, oblanceolate; pods about 

 12 mm. in diameter. P. didymocarpa lanata A. Nels. Rockj^ slopes and rolling 

 plains: n Wyo. Submont. Je-Jl. 



3. P. vitulifera Ryr'b. Stems ascending or decumbent, 1-2 dm. high; 

 basal leaves numerous, the larger 4-5 cm. long; terminal lobe nearty orbicular 

 to broadly obovate, sub-entire, obtuse; lateral lobes 1-2 pairs, much smaller; 

 petals clawed, 8-9 mm. long; fruit obtuse at the base, deeply divided above; 

 cells 5 mm. in diameter. Dry places in the mountains: Colo. Mont. My-Jl. 



4. P. floribunda Rydb. Stems numerous, ascending or almost erect, 1-2.5 

 dm. high; basal leaves less crowded and more erect than in the preceding, oblan- 

 ceolate or spatulate, sinuately toothed, usually acute, 5-10 cm. long; petals 

 bright yellow, 8-9 mm. long; fruit obtuse or slightly cordate at the base, deeply 

 divided above; cells about 8 mm. in diameter. Sandy soil, in mountain valleys: 

 Colo. Submont. — Mont. Ap-Jl. 



