H. drummondii (left) & H. reverchonii var. serpyllifolia details. (A: stem, B: peduncle, C: pedicel, D: petiole, F: bracteole)
[click to enlarge]
R. Irving's 1980 (Sida 8:257-9) article limits his description of peduncles for the H. drummondii complex taxa to:
The Hedeoma inflorescence is an axillary cyme with pedicels (& bracteoles, flowers) arising from a very short peduncle. The trichomes of the peduncle are greatly reduced, continuing a reduction in those at the base of the pedicel, more sparse than those, and generally greatly reduced on the surface against the leaf/peduncle, often appearing glabrous unless viewed under strong magnification. They are retrorsely oriented, morphologically similar to those of the pedicel & stem, thus being easily distinguished in the images below from the closely associated bracteoles, petioles & leaves.