532 



COMPOSITE. 



1. H. macradenia (DC.) Greene. Adeline Tarweed. Branch- 

 ing from above the base, about 1 ft. high; herbage unpleasantly 

 odorous; lower leaves linear-oblong, laciniate; heads ^ in. broad. 



Low dry fields about San Francisco Bay. Aug. -Sept. Connects 

 Hemizonia with Centromadia too intimately. 



49. CENTROMADIA Greene. Spikeweed. 

 Kigidly branching annuals with alternate spinescent leaves and 

 involucral bracts, the lower pinnatifid, the upper entire. Herbage 

 more or less glandular and scented. Flowers yellow, with 25 to 40 

 small bifid rays. Keceptacle with chaffy bracts throughout, none of 

 the outer united or connate. Disk-achenes chiefly sterile, with or 

 without narrowly linear or bristle-like palea?. Kay-achenes more or 

 less triangular, smooth or roughish on the back, the inner terminated 

 by an erect beak-like apiculation. (Greek kentron, a prickle, and 

 Madia, an allied genus.) 



Herbage yellowish green, sparsely hirsute, sweet- or honey-scented; floral 

 leaves little or not at all surpassing the heads 1. C. pungens. 



Herbage dark, rather densely villous-hirsute, ill-scented; floral leaves often 

 conspicuously surpassing the heads 2. C. Fitchii. 



1. C. pungens (H. & A.) Greene. Common Spikeweed. Herb- 

 age sparsely hirsute or hispid with spreading hairs, hardly viscid or 

 glandular; stems rigidly and freely branching, commonly from near 

 the base, sometimes only above, 1 to 2 or 3 ft. high; leaves (especially 

 of the flowering branches) linear-subulate, spinose, entire, the lower 

 and lowest pinnately parted into oblong lobes, or pinnatifid, the lobes 

 or teeth spinosely or pungently tipped; bracts of the receptacle cus- 

 pidate; pappus of disk none; ray-achenes roughish, somewhat laterally 

 2-nerved on back. — (Hemizonia pungens T. & G.) 



Abundant on the plains of the Lower San Joaquin, southward to 

 Southern California and westward to Walnut Creek and Alameda 

 (whence Greene's C. maritima). On the alkaline plains of the Upper 

 San Joaquin this species covers tens of thousands of acres and often 

 forms thickets 4 or 5 ft. high. It is a valued bee plant; "car-loads of 

 Spikeweed honey are shipped annually from Fresno Co.; the honey 

 is of amber color, good quality and granulates quickly," O. L. Abbott. 



Var. Parryi (C. Parryi Greene). Minutely glandular; bracts of 

 receptacle thin, not pungent; disk-achenes with 3 to 5 slender almost 

 bristle-like paleue as long as the corolla; ray-achenes semi-obcordate in 

 outline. — Calistoga; Vacaville ( = C. rudis Greene, the achenes either 

 smooth or rough warty). It is abundant in low more or less alkaline 

 lands on the plains of Solano Co. and forms extensive colonies in 

 summer fields; extermination is often accomplished by means of 

 bands of sheep which leave the fields perfectly clean and destitute of 

 this Spikeweed pest. 



2. C. Fitchii (Gray) Greene. Fitch's Spikeweed. Diffusely 

 branched from above or at the base, 9 to 10 in. high, the herbage 

 hirsute or villous with spreading hairs; leaves of the radical tuft 

 pinnately parted into remote narrowly linear pungent lobes; cauline 



