232 FOUNDATIONS OF BOTANY 



large and showy, with a yellow disk and many white rays. A trouble- 

 some but handsome perennial weed. Introduced from Europe, 

 chiefly E. 



2. C. frutescens, L. Marguerite. Erect, branching, perennial, 

 woody below, smooth, and with a pale bloom. Divisions of the 

 leaves linear, with the uppermost leaves often merely 3-cleft bracts. 

 Heads long-peduncled, showy, with a yellow disk and large, spread- 

 ing white rays. Cultivated in greenhouses ; from the Canary Islands. 



IX. SENECIO, Toum. 



Annual or perennial ; stems often hollow. Leaves alternate, 

 entire or pinnately divided. Heads wdth or without rays, in 

 terminal corymbs ; bracts mostly in a single row, often with a 

 few shorter ones at the base ; receptacle naked or pitted. Ray- 

 flowers yellow or orange, pistillate and fertile when present ; 

 disk-flowers tubular, perfect. Akenes cylindrical or com- 

 pressed, not beaked or winged, 5-10-ribbed, downy. Pappus 

 of numerous, slender, white hairs.* 



1. S. tomentosus, Michx. Woolly Ragweed. Perennial; wooUy 

 throughout ; stem stout, erect, mostly simple, 2-3 ft. high. Lower 

 leaves ovate to oblong, crenate or entire, obtuse, long-petioled; stem- 

 leaves few, elliptical to oblanceolate, serrate or toothed, acute, sessile. 

 Heads radiate, | in. wide, on slender peduncles ; bracts narrow, 

 becoming smooth. Ray-flowers 12-1.5, yellow. Akenes hairy. On 

 damp soil.* 



2. S. aureus, L. Golden Ragweed. Perennial ; stems often 

 tufted, erect, slender, woolly when young, branched above, 18-30 in. 

 high. Lower leaves broadly ovate, obtuse at the apex, heart-shaped 

 at the base, crenate, long-petioled ; stem-leaves lanceolate and often 

 pinnatifid, the upper small and sessile. Heads radiate, corymbed, 

 on slender peduncles; ray-flowers 8-12, bright yellow. Akenes 

 smooth. On wet soil ; very variable.* 



3. S. lobatus, Pars. Butterweed. Annual ; stem erect, ridged, 

 hollow, often w^ooUy when young, and becoming smooth with age, 

 branched above, 1-3 ft. high. Leaves lyrate-pinnatifid, thin, the 

 lower petioled, the upper sessile. Heads radiate in a terminal 

 corymb ; bracts linear, acute. Ray-flowers about 12, yellow. 

 Akenes slightly rough-hairy on the angles. Pappus rough, longer 

 than the involucre. Common on low ground.* 



