194 



WEEDS AND USEFUL PLANTS. 



form bristles in one or more series the inner series often smaller and 

 somewhat conniveut. Polymorphous kerbs. Leaves alternate. Heads 

 solitary, large. 



,./' 1, C, Cy'anus, L. Covered with a 



loose cottony down ; stem erect, much 

 branched ; leaves lance-linear, sessile, 

 entire the lower ones broader, taper- 

 ing into a kind of petiole, toothed or 

 pinnatifid at base ; pappus shorter 

 than the akene. 



BLUE CENTAUREA. Blue-bottle. Rag- 

 ged Robin. Blue Bonnets, of the 

 Scotch. 



Fr. Bluet. Germ. Die Korn-blume. 

 Span. Ciano. 



Root annual. Stem 1 - 2 or 3 foot high. Leaves 

 2-6 inches long, hoary-villous or lanugiuous 

 especially on the under side. Heads round- 

 ish-ovoid, pedunculate, not bractoato ; outer 

 scales of the involucre ovate-serrate, the in- 

 ner ones longer, lanceolate, scarious and en- 

 tire below, serrate near the apex. Florets of 

 the centre regular, with a slender tube, mostly 

 violet-purple, the marginal ones obsolctely 

 pistillate, larger, spreading or recurved, fun- 

 nel-form with along tube, blue, or sometimes 

 purplish or white. Akenes oblong, compress- 

 ed, striate, pilose, with a cavity (areola) on 

 one side of the base ; pappus composed of nu- 

 merous russet scabrous hairs of unequal 

 length . 



Gardens and cultivated fields : Northern 

 and Middle States : introduced. Native of Europe. Fl. July. Fr. August. 



Obs. This plant is often seen in gardens, and in some places is grad- 

 ually straggling into the cultivated fields. As it is considered a trouble- 

 some weed, among the grain crops of Europe, it may be well to watch 

 and arrest its progress here. Every worthless intruder should be regarded 

 with a jealous eye, by the farmer. C. ni'gra and C. Calci'trapa, L., are 

 naturalized to some extent ; the former, known as " Knapweed," has tho 

 scales of the involucre margined with a short black fringe and short 

 pappus principally in New England. C. Calci'trapa, or " Star Thistle." 

 has the middle scales of the involucre terminating in spines, and no 

 pappus. Virginia. 



24. CYNA'RA, Vaill. ARTICHOKE. 



[Greek, Kyon, kynos, a dog ; the spines of the involucre resembling dogs' teeth.] 



Heads many-flowered ; florets all equal. Involucre ovoid the scales im- 

 bricated, coriaceous, produced into a lanceolate appendage which is 



322 



FIG. 132. The Bluebottle (Contrmroa Cyanup). 133. A divided head, showing a marginal 

 and disk-flower remaining oa tho bristly receptacle 



