THISTLE FAMILY 



255 



Disk about 1.5 cm. wide, yellow; bracts linear-lanceolate, subequal, in about 



series. " 2. //. Parryi. 



Disk about 1 cm. broad, purple; bracts unequal, in 3-4 series. 



Ligules 5-6 mm. long. 3. //. microccphala. 



Ligules more than 1 cm. long. I. H. scabra. 



Paleae of the receptacle firm-chartaceous. 



Stem more or less hirsute, rarely glabrous; leaves tliin, not strongly reticulate. 



5. H. Doufjlasii. 

 Stem more or less scabrous-puberulent; leaves rather firm and reticulate. 



6. H. uniflora. 



77. XIMENESIA Cav. 



1. X. eiauriculala. 



78. COREOPSIS L. Tickseed. 



Leaves i)innatifld. 



Achenes winged. 1. C. Atkinsoniana. 



Achenes wingless. 2. C. tinctoria. 



Leaves simple. 3. C. lanceolata. 



79. BIDENS L. Beggar-ticks, Bur-marigold. 

 Achenes flat, obovate or cuneate; leaves or segments broad. 



Leaves pinnately 3-5-foHolate. 



Outer bracts 4-8; achenes nearly black. 1. B. frondnsa. 



Outer bracts 10-16; aclienes brown. 2. B. vulgala. 



Leaves simple. 



Heads discoid, erect; corolla 4-toothed; achenes not tubercled. 3. B. comosa. 



Heads usually radiate, nodding; corolla 5-toothed. 



Outer bracts not much longer than the inner; achenes not corky 



4. B 



Outer bracts surpassing the rays; achenes with corky angles. 



on the angles. 

 , prionophylla. 



Achenes Unear, tetragonal; leaf-segments small. 

 Divisions of the leaves oblong or lanceolate. 

 Divisions of the leaves linear. 



5. B. glaucescens. 



Bigelovii. 

 tenuisecla. 



80. THELESPERMA Less. 



Heads radiate. 



Leaf-segments linear-filiform, 1 mm. or less wide. 



Annual or biennial; outer bracts subulate-linear, more than half as long as the in- 

 ner. 1. T. Irifidum. 

 Perennial from a rootstock; outer bracts hnear-lanceolate, half as long as the 

 inner or less. 2. T. tenue. 

 Leaf-segments linear, over 1 mm. wide: plant perennial or the first only biennial. 

 Plant with a taproot, leafy throughout. 3. T intermedium. 

 Plant with a creeping rootstock or woody caudex, leafy only near the base. 



Involucre not cleft below the middle; throat of the disk-flowers campanulate. 



shorter than the lobes. 4. T. ambiguum. 



Involucre cleft below the middle; throat of the disk-flowers cylindraceous, 

 longer than the lobes. 5. T. subnudum. 



Heads discoid; perennials, with a rootstock or woody caude.Y. 



Plant less than 2 dm. liigh; involucre with very broad scarious margins. 



6. T. marginatum. 

 Plants 3-6 dm. high; involucre with very narrow scarious margins. 7. T. gracile. 



81. PTILONELLA Nutt. l. P. scabra. 



82. MADIA Molina. 

 Ray-flowers 5-12; heads not glomerate. 



Heads on short branches, racemosely disposed. 1. M. racrmoxa. 



Heads on long branches, more corymbose. 2. A/, dissiliflora. 



Ray-flowers 2-5, or none; heads glomerate. 3. A/, glomerala. 



83. HARP AE CARPUS Nutt. l. H. exiguus. 



84. HEMIZONELLA A. Gray. l. H. minima. 



85. LAGOPHYLLA Nutt. l. L. ramosissima. 



86. BLEPHARIPAPPUS Hook. l. B. glandulo.ius. 



87. PSILdSTROPHE DC. Paper Flower. 



stem merely sparingly villous or floccose, not densely white-pannose. 



Squamellae of the pappus one-third as long as tlie disk-corollas, ovate, mostly ob- 

 tuse; leaves broadly spatulate; Ugules 8-12 mm. long, indistinctly nerved. 



1. P. Bakeri. 

 Squamellae of the pappus one-half as long as the disk-corollas, lanceolate, acute or 

 acuminate; ligules 5-8 mm. long, distinctly veined. 



