1907] Hall.Compositae of Southern California. 243 



at the ends of the branches, homogamous. Bracts of the involucre 

 broad, appressed, bearing an abruptly spreading spine which is 

 broadly lanceolate or ovate and ciliate-prickly toward the base. 

 Flowers purple. Corollas with filiform tube conspicuously dil- 

 ated below the narrowly linear lobes. Pappus-bristles in several 

 series, flattish, minutely barbellate. Two species, natives of the 

 Mediterranean Region, one of them becoming naturalized in 

 California. 



1. S. Marianum (L.) Gaertn., Fruct. ii. 378 (1791). Car- 

 dmis Marianne L., Sp. PL 823 (1753). MILK THISTLE. 



Branching, 10 to 20 dm. high : lower leaves 5 dm. or more long 

 and over 1 dm. wide, sinuate-pinnatifid, strongly undulate at the 

 sinuses; upper leaves smaller, merely spinulose-toothed : heads 

 2.5 to 5 cm. broad exclusive of the stout spreading or recurved 

 spines, these often 3 cm. long. 



Sparingly introduced: Riverside; San Bernardino; Santa 

 Catalina Island; Oak Knoll and El Monte, ace. to Davidson; 

 coast of Ventura Co. 



100. CENTAUREA L. STAR THISTLE. 



Erect or diffuse usually rigid herbs with alternate leaves and 

 medium-sized or large heads. Involucre ovoid or globose, the 

 bracts imbricated and ending in a needle-like spine or in a 

 fringed or toothed (rarely entire) appendage. Receptacle dense- 

 ly bristly, the bristles persistent. Flowers all tubular, the mar- 

 ginal much larger and neutral or the heads homogamous. Achenes 

 somewhat compressed, mostly smooth, notched just above the 

 base, indicating the oblique or lateral attachment. All our spe- 

 cies naturalized from Europe. 



Flowers yellow: involucral bracts spinose. 



Plant erect, branching mostly above the base: spines .5 to 1 cm. long 

 1. C. Melitensis. 



Plant diffuse, branching from the base: spines 1 or 2 cm. long 



2. C. solstitialis. 



Flowers blue (varying to white or purple) : involucral bracts merely fim- 

 briate 3. C. Cyanus. 



