Open–head with large ligules. Closed–head with small, but visible, ligules. Closed–head with reduced ligules
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Chaptalia texana Ligulate Pistillate Florets
by Bob Harms  email-here

The greatest floret differences are found among the peripheral series of ligulate pistillate flowers. Ligule size, corolla length, pappus length vary considerably among the three major types. And one type (IV) has lengthened tubular (filiform) corollas corresponding to the ligules of the other types. Although clear differences in ligule & corolla length were to be expected, the open head also had significantly reduced pappus — providing ready access to pollinators.
  floret length corolla length* pappus length
  average range average range average
open–head (type I) 12.6 mm 11-13.2 mm same 9.4 mm
closed–head: type II 11.4 mm 10.2-12 mm same 12 mm
closed–head: type III 10.9 mm 10-11.3 mm 8.9 mm 7.9-9.3 mm 12.9 mm
*not including the style

Typical open–head (type I) florets

Variation among closed–head type II florets

closed–head type III highly reduced florets

closed–head type III corolla almost reduced to filiform tube

But the peripheral florets of type IV (and fall/winter heads of all types) are morphologically more similar to the eligulate pistillate florets, although their tubes are much longer:

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