178 KEY AND FLORA 



one series, boat-shaped, and embracing the black or brown 

 flattened akenes. Receptacle without chaffy scales in the 

 center, but with one or two rows between the disk and the 

 ray. Ray flowers and usually disk flowers without pappus. 

 Rays yellow, sometimes with a brown spot at base. 



a. M. eregans Don. Stems branching. Heads in loose panicles 

 an inch in diameter, with conspicuous yellow rays, often with a brotcn 

 spot at base. Foliage lemon-scented. Widely distributed. 



b. M. sati'va Molina. Stems simple or branching. Heads 

 usually densely clustered, with inconspicuous yellow rays. The bracts 

 enclosing the akenes persist around the akenes and adhere to other 

 substances by means of their viscidity, thus accomplishing the dis- 

 tribution of the seed. Widely distributed. 



XXHI. HEMIZO'NIA, Tarweed 



This is similar to Madia, the chief difference being the 

 bracts enclosing the akenes, which in Madia almost entirely 

 surround the individual akenes, while in Hemizonia they only 

 half enclose them. (" Hemizonia " means half zone.) The 

 disk flowers generally have pappus and the rays are either 

 yellow or white. Anthers brown. 



a. H. luzulaefo'lia DC. Annual, widely branching. Lower leaves 

 long, linear, silvery, with shining white hairs, the upper leaves very glan- 

 dular. Heads numerous, with white or yellow 3-lobed rays less than 

 j? in. long, the dark-brown anthers conspicuous. This is one of the 

 commonest Tarweeds, blooming in summer and fall. 



b. H. pun'gens (Centroma'dia) . Stems much branched, hirsute. 

 Lower leaves twice pinnatifid, with short spiny lobes, those on the 

 branchlets entire, crowded, spine-tipped. Bracts of the involucre spiny, 

 and also the narrow chaff of the receptacle. Rays about as long as the 

 disk, 2 or 3 toothed. Pappus none. This is common, blooming in 

 summer and fall. 



c. H. multiglandulo'sa Gray (Calycade'nia) . Annuals, with erect 

 stems and branches ; covered, especially above, with black tack- 

 shaped glands ; lemon-scented. Leaves narrowly linear. Heads 

 crowded in the axils of the upper leaves or sometimes solitary. 

 Flowers white or tinged with rose-color, the rays 1-7, broad, deeply 

 3-lobed. Receptacle flat, with chaffy scales only between the ray 

 and the disk flowers. Common in California. The species are 

 very numerous and difficult. 



