Var. megacarpum.- glabrous throughout, fruit 2-3 times larger than the usual (6"x4") - 1-2" high. Vittae simple & conspicuous in the intervals, a central pair in the commissure. Approaches nearly P. dasycarpum, which includes P. tormentosum of 18th. but differs in the bracteate involucelate, more capitulate umbels, & less tormentosa fruits, Vittae 6 in the commissure, 2-4 in each interval. Collected by Nuttall on Platte Plains, by Haydn in Nebraska, by Saberry in N. Mexico, by Merriam at Virginia City. = forniculatum P., 7, +9, ! cf.+ P. triforme.- var. platycarpum, Torr. in lit. - fruits seen in Herb Zoo.- fruit 6"x4", 14" high. - also flowering spring Nuttall's XII Glabrous. Fruit ranging in breadth, frequently much thickened. Whole plant with a strong rank odor. Root not strongly ridged. - Hall the only one in Nebraska. The ray of the involucre (1/4-3") mm in flower + fruit Narrower - The only other that is certainly same as mine is Geyer 220, unnamed except as certainly a Pteridium - Very possibly distinct.