COMPOSITE. (COMPOSITE FAMILY.) 247 



23. PL U CHE A, Cass. MARSH-FLEABANE. 



Heads many-flowered ; the flowers all tubular ; the central perfect, but sterile, 

 few, with a 5-cleft corolla ; all the others with a thread-shaped truncate corolla, 

 pistillate and fertile. Involucre imbricated. Anthers with tails. Achenia 

 grooved. Pappus capillary, in a single row. Herbs, somewhat glandular, 

 emitting a strong or camphoric odor, the heads in close compound corymbs. 

 Flowers purplish, in summer. (Dedicated to the Abbe Pluche.) 



1. P. camphorata, DC. (SALT-MARSH FLEABANE.) Annual, minutely 

 viscid, pale (l-2 high); leaves scarcely petioled, oblong-ovate or lanceolate, 

 thickish, obscurely veiny, serrate; corymb flat; involucre viscid-downy. (Co- 

 nyza camphorata, Bigel. C. Marylandica, Pursh.) Salt marshes, Massa- 

 chusetts to Virginia and southward. 



2. P. fOBtida, DC. Perennial, almost smooth (2 -4 high) ; leaves distinctly 

 petioled, veiny, oval-lanceolate, pointed at both ends, serrate ; corymbs panicled ; 

 involucre smooth. River-banks, Ohio to Illinois, and southward. 



3. P. bifrons, DC. Perennial; leaves closely sessile or half-clasping by a 

 somewhat heart-shaped base, lance-oblong, sharply denticulate, veiny (only 2'- 

 3' long) ; heads clustered in a corymb ; involucre smooth. Salisbury, Mary- 

 land ( W. M. Canby), and southward. 



24. BACCHARIS, L. GROUNDSEL-TREE. 



Heads many-flowered ; the flowers all tubular, direcious, viz. the pistillate and 

 staminate flowers in separate heads borne by different plants. Involucre imbri- 

 cated. Corolla of the pistillate flowers very slender and thread-like; of the 

 staminate, larger and 5-lobed. Anthers tailless. Achenia ribbed. Pappus of 

 slender capillary bristles, in the sterile plant scanty and tortuous ; in the fertile 

 plant very long and copious. Shrubs, commonly smooth and resinous or glu- 

 tinous. Flowers whitish or yellow, autumnal. (The name of some shrub 

 anciently dedicated to Bacchus.) 



1. B. halimifolia, L. Smooth and somewhat scurfy ; branches angled ; 

 leaves obovate and wedge-form, coarsely toothed, or the upper entire ; heads 

 scattered or in leafy panicles ; scales of the involucre acutish. Sea beach, 

 Massachusetts to Virginia, and southward. Shrub 6 -12 high; the fertile 

 plant conspicuous in autumn by its very long and white pappus. 



2. B. glomeru.ltfl.6r a, Pers. Leaves spatulate-oblong ; heads larger, 

 sessile in the axils or in clusters ; scales of the bell-shaped involucre broader, 

 very obtuse : otherwise like the last. Pine barrens, E. Virginia and south- 

 ward. 



25. POLi'MNIA, L. LEAF-CUP. 



Heads many-flowered, radiate: the rays several (rarely abortive), pistillate; 

 the disk-flowers perfect but sterile. Scales of the involucre in two rows ; the 

 outer about 5, leaf-like, large and spreading ; the inner small and membrana- 

 ceous, partly embracing the thick triangular-obovoid achenia. Eeceptacle flat, 

 with a membranaceous chaff to each flower. Pappus none. Tall branching 



