956 



COMPOSITAE 



Silphium 



strongly scented, odor characteristic and unpleasant; leaves thin, pinnately lobed; 

 achenes mostly 3-4 mm long, 3-ribbed and finely striated or the striae obscure. . . . 



1. P. canadensis. 



Rays yellow, 12-22 mm long; plants generally 1.5-2.5 m high; glandular only in the 

 inflorescence; leaves firm, palmately lobed; achenes mostly 6-8 mm long, coarsely 

 striated 2. P. Uvedalia. 



1. Polymnia canadensis L. White-FLOWER Leafcup. Map 2092. This 

 species is found, no doubt, in every county except possibly in a few of 

 the prairie counties. It is strictly a woodland species and prefers a moist 

 soil covered with leaf mold in thick woodland. It is rarely found on steep 

 slopes without leaf mold or in open woodland, but is often found in over- 

 flow land along streams. 



W. Vt. to Minn., southw. to N. C, Tenn., and Ark. 



la. Polymnia canadensis f. radiata (Gray) Fassett. This is a form in 

 which the ligules of the heads are fully developed, usually being about 1 cm 

 long. Found with the species but rare. 



2. Polymnia Uvedalia L. Yellow-flower Leafcup. Map 2093. Re- 

 stricted to the southern part of the state where it is found on wooded 

 slopes in places exposed to the sun, usually toward the base of a slope 

 but not always so. It is infrequent and grows in colonies. In 1931 in 

 Harrison County, I found it as a common weed in an orchard of Wm. W. 

 Jacobs about a mile west of Glidas. The orchard was on the south side 

 of a woods where the species was common and from which it had escaped 

 into the orchard. The owner was making strenuous efforts to eradicate it. 



N. Y. to Ind., southw. to Fla. and Tex. 



9131. SlLPHIUM L. Rosinweed 

 [Perry. Notes on Silphium. Rhodora 39: 281-297. 1937.] 



Stem leafless or nearly so, scaly above; very tall plants with large basal leaves. 



Leaves cordate, dentate 1. S. terebinthinaceum. 



Leaves pinnatifid or lobed. (See excluded species no. 646, p. 1099) . 



S. terebinthinaceum var. pinnatifidum. 



