THISTLE FAMILY 



255 



Disk about 1.5 cm. wide, yellow; bracts linear-lanceolate, subequal, in about 2 



series. 2. H. Parryi. 



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



Ligules 5-6 mm. long. 3, H. microcephala. 



Ligules more tlian 1 cm. long. 1. H. scabra. 



Paleae of the receptacle flrm-chartaceous. 



Stem more or less hlr.sute, rarely glabrous; leaves thin, not strongly reticulate. 



5. H. Douglasii. 

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



6. H. uniflora. 



77. XIMENESIA Cav. 



1. X. exauriculala. 



78. COREOPSIS L. Tickseed. 



Leaves pinnatifld. 



Achenes winged. 1. C. Atkinsoniana. 



Achenes wingless, 2. C. tinctoria. 



Leaves simple. 3. C. lanceolata. 



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



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

 Leaves pinnately 3-5-foliolate. 



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



Outer bracts 10-16; achenes brown. 2. B. vulgata. 



Leaves simjjle. 



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

 Heads usually radiate, nodding; coroUa 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. 



5. B. glaucescens. 

 Achenes linear, tetragonal; leaf-segments small. 



Divisions of the leaves oblong or lanceolate. 6. B. Bigelovii. 



Divisions of the leaves linear. 7. B. 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. trifidum. 

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

 inner or less. 2. T. tenue. 

 Leaf-segments linear, over 1 nun. 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 caudex. 



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



6. T. marginatum. 

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



81. PTILONBLLA Nutt. 



1. P. scabra. 



82. MADIA Molina. 



Ray-flowers 5-12; heads not glomerate. 



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



Heads on long branches, more corymbose. 2. M. dissitiftora. 



Ray-flowers 2-5, or none; heads glomerate. 3. M. glomerata. 



83. HARPAECARPUS Nutt. l. H. exiguus. 



84. HEJVIIZONELLA A. Gray. l. H. minima. 



85. LAGOPHYLLA Nutt. l. L. ramosissima. 



86. BLEPHARIPAPPUS Hook. l. B. glandulosus. 



87. PSILOSTROPHE DC. Paper Flower. 



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



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

 tuse; leaves broadly spatulate; ligules 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; hgules 5-8 mm. Jong, distinctly veined. 



