98 SPRING FLORA 



Pappus of capillary bristles; the bristles of the staminate 

 flowers more or less thickened above. Achenes oblong; terete 

 or slightly compressed. 



1. A. dimorpha Torr. & Gray. Two inches high or less, 

 caespitose. Leaves forming a small rosette; spatulate. Heads 

 solitary and subsessile at the crown, or raised on a sparsely- 

 leaved stem. Bracts of the involucre brownish. Bristles of 

 staminate flowers scarcely thickened by minute barbs; those 

 of fertile flowers long and smooth, white. Dry plains. April- 

 June. 4,000-6,000 ft. 



8. CIRSIUM. (Carduus). Thistle. 



Herbs with alternate, sessile, spiny-tipped leaves. Heads 

 many-flowered; involucres much-imbricated; outer bracts or 

 all of them spiny-tipped. Flowers (in most species) all per- 

 fect; reddish-purple, pink, whitish or rarely yellow. Anthers 

 long-appendaged at tip. Receptacle densely bristly. Pappus- 

 bristles plumose, numerous, united into a ring at the base. 



1. C. undulatum (Nutt. ) Spreng. Erect, white-woolly 

 throughout, from a biennial root; 1-4 ft. high. Leaves partly 

 clasping; wavy-pinnatifid or sometimes pinnately-parted with 

 lanceolate or triangular lobes; rather prickly; white-woolly 

 on both sides. Heads single at the end of the branches; 

 bracts with a glandular dorsal ridge; flowers purplish to nearly 

 white. Dry plains. June-August. 



9. IVA. Marsh Elder. 



Annual or perennial herbs with thick opposite( or the upper 

 alternate) leaves. Inflorescence axillary. Flowers greenish, 

 nodding, perfect. Involucre of a few rounded bracts. Marginal 

 flowers 1-6. pistillate, fertile; central flowers perfect but 

 sterile, with funnelform corollas. Anthers scarcely coherent. 



1. I. nxillaris Pursh. Perennial by woody roots; stems 

 branched or unbranched. Leaves sessile; obscurely 3-nerved; 

 from linear-oblong to obovate; mostly entire; obtuse. Heads 

 solitary in the axils, short-peduncled. In alkaline soil. May- 

 September. 



10. CHRYSOTHAMNUS, (Bigelovia). Rabbit-brush. 



Shrubs with narrow, entire leaves. Heads with 5-30 yellow 

 disk-flowers. Style-branches subulate or filiform, usually long- 

 exserted. Achenes terete or slightly angled; narrow; pubescent. 

 Pappus soft, copius; usually dull- white. 



1. C. graveolens (Nutt.) Greene. Rayless Golden-rod. Plant 

 widely bushy-branched, green and smooth or nearly so; 2-5 ft. 

 high. Leaves numerous, green on both sides; ascending, linear, 

 obscurely 3-nerved. Flowers orange-yellow; heads many in 

 a rounded cymose corymb. Dry places. June-August. 



11. MATRICARIA. Camomile. 



Herbs with finely 1-3-divided leaves. Heads peduncled; 

 with white, pistillate rays (in some species wanting), and 

 yellow, perfect disk-flowers on an elongated conical and naked 

 receptacle. Achenes 3-5 ribbed. Pappus none. 



