18 POLYGONACEAE 



serted at the base of the calyx-tube. Cotyledons accumbent, orbicular. [Name Greek, 

 meaning spiny case, in reference to the spiny involucre.] 



A genus of 8 or 9 species, inhabiting arid regions of western North America, also Chile and Argentina. 

 Type species, Oxytheca dendroidea Nutt. 



Involucres lobed. 



Involucre 4-lobed. 



Bracts united only at base; involucres mostly on slender pedicel -like peduncles. 



Leaves narrowly linear or linear-oblanceolate, acute, hirsutulose. 1. O. dendroidea. 



Leaves broadly or narrowly spatulate, rounded at apex, hispidulose, especially on the margin. 



2. O. Watsonii. 



Bracts orbicular-perfoliate, the lobes indicated only by marginal bristles. 3. O. perfoliate. 



Involucre S-lobed. 



Involucres deeply divided into narrow lobes. 



Plants prostrate; involucres sessile; the lobes of unequal length; calyx yellow. 



4. O. luteola. 



Plants erect; involucres on slender pedicel-like peduncles; calyx white or pinkish. 



Calyx-lobes entire. 5. O. caryophylloides. 



Calyx-lobes deeply cleft. 6. O. trilobata. 



Involucres a conspicuous round disk, the margin with 5 broad shallow lobes, with scarious margins. 



7. O. emarginata. 



Involucres not lobed, the tube 7-25-ribbed, each rib ending in a prominent bristle. 8. O. Parishii. 



1. Oxytheca dendroidea Nutt. Tree-like or Nuttall's Oxytheca. Fig. 1341. 



Oxytheca dendroidea Nutt. Journ. Acad. Phila. II. 1 : 169. 1848. 

 Oxytheca foliosa Nutt. Journ. Acad. Phila. II. 1: 169. 1848. 

 Eriogonum dendroideum Stokes, Gen. Eriog. 27. 1936. 

 Eriogonum dendroideum var. Hillmanii Stokes, Gen. Eriog. 27. 1936. 



Stem erect, 15-40 cm. high, dichotomously or trichotomously branched above the base, form- 

 ing a broad crown, the ultimate branchlets nearly capillary, sparsely stipitate-glandular. Leaves 

 basal, narrowly linear to linear-oblanceolate, 1 . 5-3 cm. long, acute at apex, narrowed below to 

 the petiole, hirsute especially on the midrib and margins ; involucres solitary on very slender, 

 often very short peduncles, arising from the axil of the bracts at all the nodes, turbinate, 4.5 mm. 

 long, 4-lobed, each lobe tipped by a straight spine 1-2 mm. long ; flowers 2-3, exserted on slender 

 pedicels ; calyx white or rose-colored, 1 . 5 mm. long, hispidulose. 



Sandy flats and slopes, Upper Sonoran Zone; eastern Washington, Idaho, and Wyoming south to Nevada 

 and Mono County, California. Type locality: "sandy hills, Snake River, Rocky Mountains." Nuttall. June-Sept. 



Plants apparently conspecific with this species are found in Chile and Argentina. 



2. Oxytheca Watsonii Torr. & Gray. Watson's Oxytheca. Fig. 1342. 



Oxytheca Watsonii Torr. & Gray, Proc. Amer. Acad. 8: 191. 1870. 

 Eriogonum cuspidatum Stokes, Gen. Eriog. 27. 1936. 



Stems erect, dichotomously branched above, 10-20 cm. high, glaucous, sparingly stipitate- 

 glandular. Leaves basal, broadly to narrowly spatulate, 15-25 cm. long, rounded or obcordate 

 at apex, hispidulose ; bracts connate on one side, ovate-lanceolate, awned ; involucres on slender 

 peduncles, turbinate, 1 . 5-2 mm. long, 4-lobed, each tipped with a straight awn about 2 mm. long ; 

 flowers several, pedicelled; calyx 1.5 mm. long, white, puberulent especially on the midvein. 



Dry gravelly or sandy soils, Sonoran Zones; western Nevada, and western edge of Mojave Desert (Cushen- 

 berry Springs), California. Type locality: Monitor Valley, Nevada. May-July. 



3. Oxytheca perfoliata Torr. & Gray. Perfoliate Oxytheca. Fig. 1343. 



Oxytheca perfoliata Torr. & Gray, Proc. Amer. Acad. 8: 191. 1870. 

 Eriogonum perfoliatum Stokes, Gen. Eriog. 28. 1936. 



Stems erect, widely branched from the first node, stipitate-glandular on lower half of inter- 

 nodes otherwise glabrous, usually more or less tinged with reddish purple. Leaves basal, spatu- 

 late, 1 . 5-3 cm. long, glabrous ; bracts at first node 2 or 3, small, deeply lobed ; the others con- 

 spicuous, perfoliate and nearly orbicular, 1-2 cm. broad, spine-tipped at the ends of the usually 

 3 midveins, those subtending the involucres often much reduced and acicular ; involucres solitary, 

 narrowly turbinate, 3-4 mm. long, 4-lobed to the middle, the lobes tipped by spines about 3 mm. 

 long ; flowers several ; calyx 1 . 5 mm. long, white tinged with pink, strigose. 



Sandy or gravelly soils, Sonoran Zones; Lassen County to the Mojave Desert, California, east to Nevada 

 and northwestern Arizona. Type locality: Nevada. May-July. 



4. Oxytheca luteola Parry. Yellow Oxytheca. Fig. 1344. 



Oxytheca luteola Parry, Bull. Torrey Club 10: 23. 1893. 



Gymnogonium spinescens Parry, Bull. Torrey Club 10: 23, as a synonym. 1883. 



Eriogonum spinescens Stokes, Gen. Eriog. 28. 1936. 



Stems several from the base, prostrate, 3-10 cm. long, yellowish, pubescent. Leaves at base 

 with rounded blades, 2-5 mm. long, glabrate above, white-tomentose beneath, on petioles 15-20 

 mm. long, those of the stem opposite and similar; bracts linear, acicular, 4-5 mm. long; in- 

 volucres borne at the nodes, 5-parted, the divisions unequal, linear-lanceolate, long-awned; 

 flowers several; calyx 1 mm. long, tomentose on the globose tube, the lobes glabrous, yellow. 



Alkaline soils, Sonoran Zones; San Joaquin Valley, Madera County to Kern County, and western end of 

 Mojave Desert, California. Type locality : near Lancaster, Los Angeles County, California. June-Aug. (Yellow 

 Spiny-cape.) 



