150 SELECTED WESTERN FLORA 



3. X. Macounii, Britton. 



Like the preceding but with burs almost 1 in. long and about i in. thick. 

 Lake Winnipeg. 



4. X. commune, Britton. 



Differs from the preceding by being more slender and the burs solitary 

 in the axils. Moist ground, M^n.-Alta. 



23. IVA. Marsh Elder. 



Heads small, few-several-flowered, flowers all tubular, staminate 

 and pistillate in the same heads; receptacle chaffy. Coarse, some- 

 times woody, herbs with thick leaves, mostly alternate above and 

 opposite below, and small nodding heads of greenish flowers. 



1. I. xanthifolia, Nutt. 



Annual ; stem branched, pubescent, 2-8 ft. high ; leaves almost all oppo- 

 site, ovate, irregularly dentate, long-petioled, large, often 6 in. across; 

 heads numerous, in a dense terminal spike supported by spikes rising from 

 the axils of the upper leaves ; bracts of the involucre 10, in 2 rows. A large, 

 coarse, and unsightly weed becoming very common about towns arid all 

 waste places, Man. and v/estward. 



2. I. axillaris, Pursh. 



Perennial; woody at the base, herbaceous above, simple or branched, 

 1-2 ft. high ; leaves sessile, entire, fleshy, and often glabrous ; heads solitary 

 in the axils of the leaves ; bracts of the involucre usually 5. Alkaline flats, 

 Man.-Alta. 



24. HELIOPSIS. False Stjnplower. 



Heads many-flowered, radiate; ray-flowers fertile; di-sk-flowers 

 perfect; bracts of the involucre overlapping in 2 or 3 rows; recep- 

 tacle slightly convex, chaffy, the chaff extending up around the disk- 

 flowers ; pappus none, or a few small teeth. Perennial herbs with 

 opposite, petioled, 3-ribbed, serrate leaves and large heads of 

 yellow flowers. 



1. H. sc&bra, Dunal. 



Rough, 2-3 ft. high, usually growing in clumps; leaves ovate to lance- 

 olate, short-petioled; pappus a sort of crown, or 2 or 3 small teeth. About 

 thickets, Man. and westward. 



25. BRAUNfiRIA. Purple Cone-Flowee. 



Heads many-flowered, radiate; rays numerous, sterile, drooping; 

 bracts of the involucre spreading; receptacle slightly conical, 



