In other plants, this juvenile phase lasts until the plant is old enough to flower, after which it grows with its adult morphology. The altered growth form allows the cephalium to produce axillary buds packed together with almost no stem internode between them flower production has become very cheap because the formation of another flower bud involves making only a tiny bit of relatively narrow stem. And with the spines clustered so closely together, no animal can get to the developing flower buds. Once the flower is ready to open, it absorbs water, swells and expands its petal across the spine tips, allowing pollinator access to the nectar with some protection against the spines. After pollination, the ovules develop deep in the cephalium, and when the seeds are mature, the ovary quickly swells, pushing itself up above the spine tips.
All growth is as an adult, a cephalium.
After conversion to the adult phase, the plant can continue to flower year after year, but all chloroplasts, all photosynthetic tissues simply become older and older, and presumably less effective. This exotic life style must have profound consequences for population biology and ecology, but to my knowledge, it has not been studied. These plants grow as juveniles for several years, but when they become old enough to undergo the conversion to the adult phase, only part of the body changes. The plants have ribs, and only a few ribs are affected, only a few ribs go through puberty. All ribs are more or less similar as they are produced by the shoot apical meristem, but those that will be part of the lateral cephalium alter their morphogenesis and develop as if they were part of a terminal cephalium with close- packed nodes, spines and so on.