194 



WEKDS AND USEFUL 



PLANTS. 



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

 somewhat connivent. Polymorphous kerbs. Leaves alternate. Heads 

 solitary, large. 



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

 loose cottony down ; stem erect, much 

 branched ; leaves lance-Hnear, sessile, 

 entire — the lower ones broader, taper- 

 ing into a kind of petiole, toothed or 

 piunatifid at base ; pappus shorter 

 than the akene. 



Blue Centaurea. Blue-bottle. Rag- 

 ged Robin. Blue Bonnets, of the 

 Scotch. 



Fi . Bluet. Germ. Die Korn-blume. 

 Span. Ciano. 



i^ooi annual. (Sim 1 - 2 or 3 feet high. Leaves 

 2-6 inches long, hoary-villous or lanuginous 

 — especially on the under side. Heads round- 

 ish-ovoid, pedunculate, not bractcate ; 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 obsoletely 

 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) ou 

 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 the 

 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. Aetichoke. 



[Greek, Kyon, Tcynos, 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 



Fig. 132. The Bluebottle (Centaurea Cy anus). 133. A divided head, showing a marginal 

 and disk-flower remaining on the bristly receptacle 



