COMPOSITE. (COMPOSITE FAMILY.) 209 



25. POI^MNIA, L. LEAF-CUP. 



Heads many-flowered, radiate; the rays several, pistillate and fertile; 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 membranaceous, 

 partly embracing the thickened round-obovoid achenia. Receptacle flat, with a 

 membranaceous chaff to each flower. Pappus none. Tall branching peren- 

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

 site, or the uppermost alternate, lobed, and with dilated appendages like stipules 

 at the base. Heads in panicled corymbs. Flowers light yellow. (Dedi- 

 cated to one of the Muses, for no imaginable reason, as the plants are coarse 

 and inelegant.) 



1. P. CaJiadensiS, L. Clammy-hairy; lower leaves deeply pinnatifid, 

 the uppermost triangular-ovate and 3 - 5-lobed or angled, petioled ; rays fao, 

 obovate or wedge-form, shorter than the involucre, whitish-yellow. Moist shaded 

 ravines, W. New York to Wisconsin, and southward along the mountains. 

 July - Sept. 



2. P. Uvedalia, L. Roughish-hairy, stout (4 -10 high) ; leaves broadly 

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

 narrowed into a winged petiole ; outer involucral scales very large ; rays 10-15, 

 linear-oblong, much longer than the inner scales of the involucre, yellow. Rich soil, 

 W. New York to Illinois and southward. Aug. 



26. CIIRYSOGONUM, L. CHRYSOGONUM. 



Heads many-flowered, radiate ; the rays about 5, pistillate 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 concave 

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

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

 short scale of the involucre behind it ; those of the disk-flowers abortive. Pap- 

 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, crenate, 

 long-petiolcd. Heads single, long-peduncled. Flowers yellow. (Name com- 

 posed of xpucros 1 , golden, and yow, knee.) 



1. C. Virgiiiiamun, L. Dry soil, from Pennsylvania (Mcrcersburg, 

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



2?. SILPHIUM, L. ROSIN-PLANT. 



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

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

 Scales of the broad and flattish involucre imbricated in several rows, broad and 

 with loose leaf-like summits, except the innermost, which are small and resero. 

 ble the linear chaff of the flat receptacle. Achenia broad and flat, obcompressed, 

 surrounded by a wing which is notched at the top, destitute of pappus, or with 

 2 teeth confluent with the winged margin : achenia of the disk sterile and stalk- 

 18=* 



