COMPOSITE. 105 



17. Caca'lia. Flowers white or whitish. Heads 5-flowered, rather' 



large, i flat corymbs. Involucre 5-leaved. Receptacle naked, 

 bearing a scale-like pointed appendage in the centre. Corolla 

 deeply 5-clef t. Pappus of numerous capillary bristles. 



18. lya. Marginal pistillate florets 1-5, with very small tubular 



corolla or none. Staminate florets with funnel-form 5-toothed 

 corolla. Anthers nearly separate. Achenes very short. 

 Coarse plants with small greenish-white nodding heads. N. W. 



it. Rays or strap-shaped corollas round tbe margin of the head. 



* Pappus of hair-like bristles. Receptacle naked. 



19. Sene'clo. Rays yellow, or in one species none. Scales of the 



involucre in a single row, or with a few bractlets at the base. 

 Pappus very fine and soft. Heads corymbose. Leaves alter- 

 nate. 



20. In iila. Rays yellow, numerous, very narrow, in a single row^ 



Outer scales of the involucre leaf -like. Anthers with two tails 

 at the base. Stout plants, with large alternate leaves which 

 are woolly beneath. 



21. Chrysop'sls. Rays yellow, many. Disk yellow. Pappus double, 



the outer of very small chaffy bristles, the inner capillary. 

 Low hairy herbs. N.W. only. 



22. Aplopap'pns. Rays yellow, many. Disk yellow. Pappus sim- 



ple, of unequal bristles. N.W. only. 



23. Sollda'go. Rays yellow, few, as are also the disk-florets. Invol- 



ucre oblong, scales of unequal lengths, appressed. Achenes 

 many-ribbed. Heads small in compound racemes, or corymbs. 

 Stems usually wand-like. Leaves alternate. 



24. Ar'nlca. Rays yellow. Disk yellow. Scales of the bell-shaped 



involucre in two rows, lanceolate, erect. Receptacle flat, min- 

 utely fringed. Achenes slender. Leaves opposite. Heads 

 showy, with long peduncles. Stem simple. 



25. Tusslla'go. Rays yellowish, in several rows, very narrow. 



Involucre nearly simple. Pappus copious, soft. A low peren- 

 nial, with creeping rootstocks, sending up a scaly scape in early 

 spring bearing one head, and producing later heart-shaped, 

 angled or toothed leaves, woolly when young. 



26. Petasl'tes. Rays whitish or purplish. Heads in a corymb, fra- 



grant. Scales of the involucre in a single row. Heads some- 

 what dioecious, the staminate with one row of pistillate ray- 

 flowers, the pistillate with ray-flowers in many rows. Wool'iy 

 herbs, with large leaves, all radical, and sheathing scaly bracts 

 on the scape. 



