I20 Introduction to Botany. 



Involucre of i row of bracts, subtended by a few bractlets. Receptacle 

 flat and naked. Annual or perennial herbs, with solitary or corymbed 

 heads. Achenes mostly cylindrical, 5-10-ribbed, downy. 



I. Senecio lobatus, Pers. (Gr., loios, lobe.) BurrERWEED or Cress-leaved 

 Groundsel. Glabrous or only slightly woolly annual, i to 3 feet high. Leaves 

 pinnately divided, the lower ones pelioled. Heads rather more than ^ inch 

 broad, numerous in terminal corymbs. Rays 6-10, conspicuous. Involucre nearly 

 cylindric, usually with no smaller outer bracts. In wet grounds. 



a. Senecio aureus, 1-. (L., aureus, golden yellow.) Golden Ragwort or 

 Squaw Weed. Nearly or quite glabrous perennial, i to 2i feet high. Basal 

 leaves long-petioled, rounded or nearly heart-shaped, crenate. Stem leaves vary- 

 ing from lyrate below to lanceolate above, and more or less pinnatifid, sessile, 

 and clasping. Heads j of an inch or more broad, borne on slender peduncles in 

 an open corymb. Rays 8-12, yellow. This species is quite variable. Var. obovatus, 

 T. & G., has basal leaves round-obovate, the earliest being almost sessile and tufted. 

 Var. BahamltcE, T. & G., has spatulate, oblong, or lanceolate basal leaves, lyrate, 

 pinnatifid upper leaves, and heads small and numerous. In moist, open ground. 



II. LiguliflorcE, 



VII. TRO'XIMON. 



Perennial or annual herbs, with leaves tufted at the base, li'near or 

 lanceolate and entire. Heads of ligulate flowers large, yellow or rarely 

 purple, borne singly at the end of a naked or sometimes bracted scape. 

 Scales of the involucre imbricated in 2-3 rows. Receptacle flat, naked, 

 or pitted. Achenes beaked, or sometimes beakless, lo-ribbed. Pappus 

 of many rigid capillary bristles. 



1. Troximon cuspiditum, Pursh. (L,, cuspidatus, pointed.) Scape i foot 

 high. Leaves lanceolate, elongate, and tapering, entire, woolly on the margins. 

 Achenes beakless. Plains. 



2. Troximon glaucum, Nutt. (Gr., glaukos, bluish gray.) Scape i to 2 feet 

 high. Leaves oblong or lanceolate, entire, or sometimes dentate or pinnatifid. 

 Heads i to 2 inches wide. Achenes prominently beaked. Plains. 



VIII. TARAXACUM. Dandelion. 

 (Gr., tarassOy to disquiet, in allusion to medicinal properties.) 



Perennial or biennial herbs from a thickened tap-root. Heads large, 

 many-flowered, solitary on the summit of a slender, hollow scape, which 

 exudes a milky secretion when broken. Sca'es of the involucre in 2 

 rows, the outer scales short, reflexed with age, those of the inner row 



