FLOWERING PLANTS AND FERNS OF ARIZONA 913 



1. Aphanostephus humilis (Benth.) A. Gray, PL Wright. 1: 93. 1852. 



Leucopsidium humile Benth., PI. Hartw. 18. 1839. 

 Aphanostephus arizonicus A. Gray, Amer. Acad. Arts and Sci. 



Proc. 16: SI. 1880. 



Near Winkelman, Sacaton, and Red Rock (Pinal County), Benson 

 (Cochise County), 1.200 to 3.500 feet, river banks and plains, March 

 to September, type of .4. arizonicus collected on the Gila River 

 (Rothrock). Texas to southern Arizona, south to Mexico. 



22. GREENELLA 



Low, slender, branching:, glabrous, winter annuals: leaves alternate, 

 linear to lanceolate, entire; heads small, scattered or somewhat 

 corymbose, radiate or discoid, the rays when present white; involucre 

 few-seriate, the phyllaries chartaceous, scarious-margined. green- 

 tipped; achenes villous or glabrous; pappus a dissected hyaline crown. 



Key to the species 

 1. Rays present, white; ovaries and achenes densely canescent-pilosulous. 



1. G. ARIZOXICA. 



1. Rays none; ovaries glabrous or minutely puberulous 2. G. discoidea. 



1. Greenella arizonica A. Gray, Amer. Acad. Arts and Sci. Proc. 16: 



81. 1880. 



Pinal and Pima Counties. 1.400 to 4.000 feet, gravelly soil on mesas 

 and plains, March to September, type from near Tucson {Greene in 

 1877). Southern Arizona and northern Mexico. 



2. Greenella discoidea A. Gray, Amer. Acad. Arts and Sci. Proc. 19: 



2. 1SS3. 

 Known only from the type collection in Tanner Canyon, Huachuca 

 Mountains. Cochise County (Lemrnon . September. 



23. ACHAKTOGKROX 



Plant annual (?) ; stems several, about 15 cm. high, ascending', leafy 

 except toward the apex, 1- to few-headed, spreading-pilose below, 

 ascending- or appressed-pilose above; leaves spatulate to linear, entire: 

 heads medium-sized, the rays white, the disk yellow; involucre about 

 2-seriate, subequal, pilose, of thin lanceolate phyllaries with a greenish 

 midline; achenes compressed. 2-nerved, puberulous; pappus a minute 

 setulose crown. 



1. Achaetogeron chihuahuensis Larsen in Blake. Wash. Acad. Sci. 



Jour. 30: 470. 1940. 

 White Mountains, southern Apache County [Zuck in 1907, Goodding 

 539). Eastern Arizona and Chihuahua. 



24. PSILACTIS 



Slender branching annuals, glandular at least above; leaves alter- 

 nate, entire to pinnatifid; heads radiate, small, the rays white to 

 purplish, the disk yellow; involucre few-seriate, graduated, the phyl- 

 laries herbaceous at least at tip; ray achenes epappose; disk achenes 

 with a pappus of capillary bristles. 



