958 



COMPOSITAE 



Silphium 



Silphium 



~T(5 

 Map 2096a 

 laciniatum L var 



Robin sonii Perry 



3a. Silphium laciniatum var. Robinsonii Perry. (Rhodora 39: 297. 

 1937.) Map 2096a. In Indiana this variety has the same habitat as the 

 species. 



Ind., southw. to La. 



4. Silphium trifoliatum L. Whorled Rosinweed. Map 2097. Infre- 

 quent to rare in dry soil on open, wooded slopes in two widely separated 

 parts of the state. Beyond the area shown on the map, it has been reported 

 from Carroll, Cass, Knox, and La Porte Counties. This species, like the 

 next, is variable and in certain forms it is separated from it with diffi- 

 culty. In the typical form, the leaves are lanceolate, dark green, some 

 whorled, and generally with nearly entire margins. Non-typical plants 

 may have only opposite leaves or some alternate ones, and narrow-ovate 

 blades. The inner face of the achenes is glabrous or pubescent, usually the 

 latter. 



Pa., Ont., Ind., southw. to N. C. and Tenn. 



4a. Silphium trifoliatum var. latifolium Gray. This is a glabrate form 

 of the species and is not well marked. Some specimens will have most 

 of the leaves glabrous above and one or more scabrous above. I have this 

 form from Crawford, Decatur, and Washington Counties. 



Ohio and Ind., southw. to S. C. and Ala. 



5. Silphium integrifolium Michx. ENTIRE-LEAF RosiNWOOD. Map 2098. 

 Infrequent to rare, rarely frequent, throughout Indiana although there 

 are no records from the northeastern part. It is generally found in 

 dry soil on open wooded slopes, frequent in prairie habitats, and on the 

 low wooded dunes along Lake Michigan. The plants are variable in the 

 width and margins of the leaves and in the pubescence of the stem, leaves, 

 and involucre. Some plants have stems with a few ternate or alternate 

 leaves. The inner face of the achenes is either glabrous or pubescent, 

 mostly more or less pubescent. I have had all forms of this species under 

 cultivation for many years to study them. 



Ohio to Minn., southw. to Miss, and Tex. 



