248 COMTOSIT.E. (COMl'OSITE FAMILY.) 



perennial herbs, viscid-hairy, exhaling a heavy odor. Leaves large and thin, 

 opposite, or the uppermost alternate, lobed, and with dilated appendages like 

 stipules at the base. Heads in panicled corymbs. Flowers light yellow ; in 

 summer and autumn. (Dedicated to the Muse, Poli/hi/mnia, for no obvious 

 reason, as tlie ])l.ints are coarse and inelegant.) 



1. P. Canadensis, L. Clammij-hnirn ; lower leaves deeply pinnatifid, the 

 uppermost tn;ingular-ovatc and 3-5-lobed or angled, petioled; heads small; 

 rays/ew, obocate or widtjr-fnrni, shorter than the involucre, whiti-h-ycllow. — Moist 

 shaded ravines, W. New York (and Weehawken, New Jersey, Dr. Allen) to 

 Pcnn., Wisconsin, and southward along the mountains. — Var. niscoiDEA has 

 the corolla of the ray-flowers reduced to a mere ring around the base of the style. 

 Mt. Carroll, Illinois, Flcnri/ Shinier. 



2. P. Uved^lia, L. Roiujhish-hnin/, stout {A° -10° hh^h) ; leaves broadly 

 ovate, angled and toothed, nearly sessile ; the lower palmately lobed, abruptly 

 narrowed into a winged petiole; outer involucral scales very large; rai/s 10-15, 

 linear-ohlom/, i>iitch loiifjer than the inner scales of the incoliicre, } ellow. — Rich soil, 

 W. New York and New Jersey to Illinois and southward. 



26. CHRYSOGONUM, L. Ciirysogoxum. 



Heads many-flowered, radi;ite ; the rayt about 5, ])istillate and fertile ; the 

 disk-flowers perfect but sterile. Involucre of about .5 exterior leaf-like oblong 

 scales, which exceed the disk, and as many interior shorter and chaff-like con- 

 cave scales. Receptacle flat, with a linear chaff to each disk-flower. Achenia 

 all in the ray, obovate, obeompressed, 4-angled, each one partly enclosed by the 

 short scale of the involucre behind it; those of the disk-flowers abortive, l^^p- 

 pus a small chaffy crown, 2 -3-toothed, and split down the inner side. — A low 

 (2' -6' high), hairy, perennial herb, nearly stemless when it begins to flower, 

 the flowerless shoots forming runners. Leaves opposite, ovate or spatulate, cre- 

 nate, long-pctioled. Heads single, long-])edunclcd. Flowers yellow. (Name 

 composed of XP'J"''''^^ fplden, and yow, knee.) 



1. C. Virgini^num, L. Dry soil, from Pennsylvania ( Mercersburg, 

 prof. Porter) and Illinois southward. May- Aug. — Rays ^' long. 



27. SILPHIUM, L. Rosin-Plaxt. 



Heads many-flovvercd, radiate ; the rays numerous, pistillate and fertile, their 

 broad flat ovaries imbricated in 2 or 3 rows ; the disk-flowers apparently perfect, 

 but with undivided style, and sterile. Scales of the broad and flatfish involu- 

 cre imbricated in several rows, broad and with loose leaf-like sunmiits, e.\cc|it 

 the innermost, which are small and resemble the linear chaff of the flat recep- 

 tacle. Achenia broad and flat, obc()mi)resscd, surrounded by a wing which is 

 notched at the top, destitute of ])appus, or with 2 teeth confluent with the 

 winged margin: achenia of the disk sterile and stalk-like. — Coarse and tall 

 rough pcrenniid herbs, with a cojiious resinous juice, and large coryuibosc- 

 panicled yellow-flowered heads. (SiX^toi/, the ancient name of a plant which 

 produced some gum-resin, perhaps assafcutida, was transferred by Linna;us to 

 this American genus.) 



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