CABDUACEAE. 



395 



3. Leptilon pusillum (Nutt.) 

 Britton. Smooth Horseweed. 

 (Fig. 433.) Glabrous or nearly 

 so; stems slender, 3° higli or less. 

 Leaves linear to oblanceolate, en- 

 tire, or the lower sometimes witli 

 2 or 3 teeth near the apex, eiliate 

 toward the base; heads few or 

 numerous; involucre much like 

 that of the preceding species, but 

 glabrous or nearly so, its bracts 

 commonly purplish-tipped. [Erig- 

 eron pusillum Nutt.] 



Common in waste and culti- 

 vated grounds, often growing inter 

 mixed with L. canadense. Natural- 

 ized. Native of ttie eastern United 

 States, ttie West Indies and trop- 

 ical continental America. Flowers 

 nearly throughout the yeaf. 



9. SENEOIO [Tourn.] L. 



Annual or perennial herbs (some tropical &-pecies shrubby or even arbo- 

 rescent), with alternate or basal leaves, and many-flowered heads, of both 

 tubular and radiate, or only tubular flowers, in our species yellow. Involucre 

 cylindric or campanulSte, its principal bracts in 1 series, usually with some 

 shorter outer ones. Eeceptacle mostly naked. Rays, when present, pistillate, 

 fertile. Disk-flowers perfect, fertile, their corollas tubular, the limb 5-toothed 

 or 5-lobed. Anthers obtuse and entire at the base, or rarely slightly sagittate. 

 Achenes terete, or those of the marginal flowers somewhat compressed, 5-10- 

 ribbed, papillose, or canescent, at least after wetting, and then usually emitting 

 a pair of spiral threads. Pappus of numerous slender or capillary, mostly 

 white bristles. [Latin, senex, an old man, referring to the hoary character of 

 some species, or to the white pappus.] An immense genus of probably at least 

 1200 species, of very wide geographic distribution, the following typical. 



