Figure 12. Silphium perplexum and its relatives. 

A-C, S. glutinosum, Bibb County, Alabama: A. Habit, including open inflorescence; "Desmond's Glade," 9 September 1993. B. Head, frontal view, with the normal 13 rays; "Goat Glade South," 14 June 1992. C. Head, lateral view, showing outer phyllaries the longest and with recurving margins; "Brown's Dam North Glade West," 3 July 1992. 

D-F, S. perplexum: D. Habit; Perry County, Alabama, Co. Rd. 6, 19 August 1999. E. Heads, frontal view, showing maximal no. of rays per head; same date and location as in D. F. Head, three-quarters view showing the species' comparatively "ordinary" involucre; Dallas County, Alabama, type locality, 18 August 1999. 

G-I, S. integrifolium: G. Habit, including more numerous nodes, Lowndes County, Mississippi, Alt. U.S. Hwy. 45, 9 August 1992. H. Heads, frontal view, with numerous rays; Sumter County, Alabama, Ala. Hwy. 17, 19 August 1999. I. Comparatively congested inflorescence, same date and location as in G.