With strap-shaped flowers: some Asteraceae have tubular (regular) flowers in the center of the head, and strap-shaped flowers (ray flowers) along the margin....
...such as the daisies, where the strap-shaped flowers are white..:
... several other species whose flowers are all yellow...
...or some species of Achillea
, where the flowers are all white:
Without strap-shaped flowers: in this case the flowers are all regular (tubular)...
We can distinguish at least 2 types of tubular flowers: in some cases they are very short, such as in Artemisia
and in some species of Senecio
...in other cases the flowers have a long tube and long lobes, such as those of thistles: