Early stage of C. texana fruit: achene + pappus bristles (which surround the floret)
Mature C. carduacea achene, with inner pistillate floret surrounded by pappus bristles.
Fruit of Chaptalia texana and C. carduacea
by Bob Harms
Chaptalia fruits consist of an achene, attached to the head's receptacle, topped with numerous (75—200) long (8—13 mm) bristles, the pappus, which are attached around the outside of a ring (annulus) at the top of the achene's ‘beak’; the floret is attached in the center of this ring. The achene body, ‘beak’, and pappus all continue to develop from the onset of anthesis until dispersal, but most prominent is the lengthening of the beak as the achene matures, as can be noted above. The pappus also lengthens and eventually exceeds the length of the pistillate florets, which it then envelops until dispersal.
In the four sets of images below (A—D) are shown: A. C. texana: bud stage achenes with hardly any beak; B—C, C. carduacea: B, early anthesis, beak somewhat extended and pappus base not well developed, not yet straight; C: advanced achenes, with long pappus and well–developed ridges on the achene body; D: advanced achenes, with beaks extending above the involucre. (For another comparison of early and late stages.)
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| A. C. texana | B. C. carduacea | |
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| C. C. carduacea | D. C. carduacea | |||
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The achene body is fusiform (i.e. narrower at both ends than at the center) with 4–6 ribs and covered with short papillate trichomes (hairlike epidermal outgrowth).
