How do disciform flower heads differ from radiate flower heads?

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English daisies — Asterales True, or English, daisy (*Bellis perennis*).

In the family Asteraceae, flower heads are categorized by the types of florets they contain. The primary difference between these two types is as follows:

Radiate heads feature disk flowers in the center, which are surrounded by one or more marginal rows of ray flowers. These ray flowers possess an irregular, strap-shaped corolla (the ligule) that gives the head its petal-like appearance.1
Disciform heads are considered a specialized derivative of the radiate type. While they resemble discoid heads because they lack the prominent, showy marginal rays, they differ by having outer flowers that are pistillate (female) with a tubular, rayless corolla.1

Essentially, while a radiate head uses distinct, elongated ray flowers to create a showy border, a disciform head lacks these ligules, instead utilizing tubular, rayless pistillate flowers at the margin.1