Figure 4.

Scanning electron microscopy analysis of dandelion florets at young developmental stages. (A) Part of a capitulum of stage 5 (Table 1), with all floral organs formed, the petals covering the top of the florets, and the carpels lower than the anthers. Pa (green) = pappus; Pe (red) = petals; An (yellow) = anthers (stamen); Ca (pink) = carpels (pistil). (B) Some florets of stage 6, showing organ elongation, and the carpels past the anthers. Green lines indicate part of the pappus ring initiation zone at the base of the petals, with a recently initiated pappus part on top. (C) The same florets of B viewed from the top, showing 2–3 rows of pappus parts separated from the corolla. (D) Floret of stage 5, showing that pappus parts (green arrows) located at the petal fusion zones (red arrows), the alternipetal position where the sepals are expected (Figure 3), are ahead in growth. (E) Floret of stage 7, confirming the growth advance of pappus parts located at the petal fusion zones, and showing relatively increased growth of the pappus parts; the ovary and beak start to pronounce. (F) Floret of stage 8, with mature pappus parts on which scales have started to form, a pronounced pappus ring, and a clearly formed beak (Be) and ovary (Ov), with vertical lines on the fruit. (G) Fruit/Floret of stage 10, showing the elongated beak and ovary and horizontal lines on fruit. © Bertie Joan van Heuven.