CAKDUACEAE 1179 



21. GUTIERREZIA Lag. 



Annual or perennial herbs or shrubby plants, commonly with glutinous foliage. 

 Leaves alternate : blades narrow, entire. Heads radiate, often numerous, mostly in 

 crowded terminal corymbs. Involucres campanulate to turbinate or oblong-clavate, few- 

 many-flowered : bracts leathery, in few series. Receptacle small. Kay-flowers few, 

 pistillate. Disk-flowers perfect, or some of the central ones staminate. Corollas yellow. 

 Anthers obtuse at the base. Stigmas flattened, the appendages narrow. Achenes oblong 

 or obovate, terete or 5-angled. Pappus of many scales, at least in the disk, that of the ray 

 smaller than that of the disk and occasionally wanting. 



Pappus of the rays, and the disk-flowers similar or nearly so. 

 Perennial plants : heads in clustered or panicled cymes. 



Involucres over 4 mm. high, with 3-6 flowers in both disk and ray. 1. O. Sarothrae. 



Involucres less than 3 mm. high, with usually 1 or 2 flowers in both disk 



and ray. 2. O. microcephala. 



Annual plants : heads terminating the branches singly, and paniculate. 



Pappus of 5 or 6 partially united ovate scales. 3. O. sphaerocephala. 



Pappus of 12 or more narrow mostly distinct scales. 4. G. eriocarpa. 



Pappus wanting in the ray-flowers. 5. G. Texana. 



1. Gutierrezia Sarothrae (Pursh) Britt. & Rusby. Perennial, glabrous or some- 

 times pubescent. Stems often bushy, 2-6 dm. tall : leaf-blades narrowly linear, 2-6 cm. 

 long, acute : heads numerous, short-peduncled or several together in clusters and sessile : 

 involucres 4-5 mm. high, commonly 6-12-flowered ; bracts oblong, concave, obtuse : 

 achenes 1-1.5 mm. long : pappus of both the ray and disk similar or nearly so. 



In dry soil, Manitoba to Minnesota, Texas, Mexico and California. Summer. 



2. Gutierrezia microcephala (DC.) A. Gray. Perennial, glabrous or sparingly 

 fine-pubescent. Stems slender, 2-5 dm. tall, more or less branched : leaf-blades narrowly 

 linear or linear-filiform, 1-4 cm. long : heads numerous : involucres 2.5-3 mm. high, 2-4- 

 flowered : bracts fewer and narrower than in G. Sarothrae. 



On rocky plains and hills, southern Texas to southern California and adjacent Mexico. Summer. 



3. Gutierrezia sphaerocephala A. Gray. Annual, glabrous or nearly so. Stems 

 branched, 2-5 dm. tall : leaf-blades linear, narrowly so above, 1-5 cm. long, acute : heads 

 numerous, terminating the branches singly and paniculate : involucres hemispheric or 

 obovoid-hemispheric, 4 mm. high ; bracts linear or oblong, acute or acutish, often green- 

 tipped : achenes about 2 mm. long, densely pubescent : pappus of the ray and disk similar, 

 of 5 or 6 ovate, crown-like partially concreted scales barely \ as long as the achene. 



On plains and prairies, Arkansas, Texas and New Mexico. Summer. 



4. Gutierrezia eriocarpa A. Gray. Similar to G. sphaerocephala, but commonly 

 lower. Stems branched, often widely so : pappus of 12 or more linear-lanceolate or subu- 

 late mostly distinct scales about as long as the achene. 



On plains and prairies, southern Texas and adjacent Mexico. Summer. 



5. Gutierrezia Texan a (DC. ) T. & G. Annual, puberulent or glabrate. Stems 3- 

 9 dm. tall, effusely branched : leaf-blades narrowly linear or linear-filiform, 1-4 cm. long, 

 acute : heads numerous : involucres turbinate -campanulate, 2-3 mm. high, 16-20-flowered ; 

 bracts oblong to linear, obtuse or acutish : achenes fully 1 mm. long, hairy : pappus want- 

 ing in the ray, that of the disk consisting of ovate or subulate scales shorter than the thick- 

 ness of the achene. 



On plains, Arkansas and Texas. Summer. 



22. AMFHIACHYRIS DC. 



Annual or perennial caulescent herbs, with glabrous foliage. Leaves alternate : blades 

 narrow, entire. Heads very numerous, radiate. Involucres hemispheric to ovoid, few- 

 many-flowered : bracts leathery, in few series. Receptacle naked. Kay-flowers pistillate 

 and fruit producing. Disk-flowers usually perfect but not fruit producing. Stigmas flat- 

 tened, the appendages lanceolate. Achenes pubescent. Pappus various ; that of the ray 

 crown-like or obsolete ; that of the disk of 5-20 subulate or awn-like scales, often slightly 

 united at the base. 



1. Amphiachyris dracunculoides (DC.) Nutt. Annual. Stems 3-7 dm. tall, 

 effusely branched above : leaf-blades narrowly linear to linear-filiform above, 1-5 cm. long, 

 acute: heads solitary at the ends of slender' branches : involucres hemispheric, 3-4 mm. 

 high ; bracts ovate, oblong or oval, acute, lustrous : disk-flowers 10-20, each with a sterile 

 ovary and bristle-like pappus-scales united at the base : ray-flowers 3-10 ; ligules yellow, 

 oblong or oval, 3-4 mm. long : achenes of the ray-flowers with a crown-like pappus. 



On plains, Missouri and Kansas to Texas. Summer and fall. 



