SUNFLOWER FAMILY. 455 



64. AMBROSIA L. Ragweed. 



Ours a coarse homely but aromatic perennial herb with alternate pinnatifid 

 leaves and inconspicuous greenish unisexual flowers. Heads of staminate 

 flowers disposed in erect catkin-like racemes: — involucres broadly turbinate; 

 receptacle of at least the outer flowers with slender bracts; corollas funnel- 

 form, 5-lobed. Heads of pistillate flowers in the axils of the upper leaves at 

 the base of the staminate racemes: — involucres oblong or turbinate, closed, con- 

 taining but a single flower; corolla none; pappus none; fruit an achene-like bur 

 which is beaked or pointed and is armed near the top with a single row of 

 prickles. (Ancient Greek name.) 



1. A. psilostachya DC. Western Ragweed. Stems simple, erect, 1, 2 or 

 more ft. high, from slender running rootstocks; herbage pubescent and some- 

 what strigose; leaves once or the lower twice pinnatifid; fruit an obovoid 

 turgid bur, mostly solitary in the axils, bearing 4 protuberances or sometimes 

 unarmed. 



Uncultivated lands in the Sacramento Valley, eastward and southward ; 

 common about San Francisco Bay. Sept. -Oct. 



65. FRANSERIA Cav. 

 Branching herbs, ours perennial,' sometimes woody at the base. Leaves chiefly 

 alternate. Habit, flowers and inflorescence as in Ambrosia. Involucre of the 

 pistillate heads closed, 1 to 4-celled, 1 to 4-beaked or pointed, armed with 

 several rows of prickles and in fruit becoming a bur. (Ant. Franser, Spanish 

 botanist.) 



Leaves twice or thrice pinnatifid or pinnately parted 1. F. bipinnatifida. 



Leaves (at least the upper) undivided and merely serrate 2. F. chamissonis. 



1. F. bipinnatifida Nutt. Stems procumbent, herbaceous, 2 or 3 ft. long, 

 somewhat hirsute; leaves twice or thrice pinnately parted into oblong lobes, 

 canescent or almost silky; spikes dense; bur narrowly ovate, armed with thick 

 somewhat flattened spines, some of which are curved at the tip. 



Common on sandy seabeaches along the coast, and also at Alameda and 

 West Berkeley. Aug.-Oct. 



2. F. chamissonis Less. Habit of the preceding; leaves narrowly ovate 

 or obovate, with cuneate base, serrate, or the lower laciniate or incised; bur 

 thicker, sparsely hirsute, the spines broader and channeled. 



Seabeaches along the coast; less common. 



66. XANTHIUM L. 

 Coarse (by some called vile) annual weeds with widely branching and very 

 stout stems. Leaves alternate, toothed or lobed, petioled. Heads unisexual, 

 composed of greenish flowers. Staminate heads subglobose, in a terminal 

 cluster: — involucre of several distinct narrow bracts in a single row; recep- 

 tacle cylindrical; flowers many, separated by the bracts of the receptacle; 

 corolla tubular. Pistillate heads axillary, below the staminate: — involucre 

 closed, forming in fruit an ovoid or oblong indurated bur covered all over with 

 hooked prickles, 1 or 2-beaked, 2-celled, each cell containing 1 flower; corolla 

 none; pappus none; style 2-cleft, its branches exserted through the beaks. 

 (Greek xanthion, yellow, from its yielding a hair-dye of that color.) 



Leaves deltoid-ovate; stems not spiny 1. X. canadense. 



Leaves lanceolate; stems bearing spines by the sides of the leaves 2. X. spinosiun. 



1. X. canadense Mill. Cockle Bur. Stems about 2 ft. high, not prickly; 

 leaves deltoid-ovate or somewhat cordate, irregularly serrate, or somewhat 



