Several flower types occur in the angiosperms. The main classifications are briefly discussed below.
Complete vs. Incomplete Flower Types
There are four tissues all or some of which make up a flower as a structural organ in the angiosperms: sepal, petal, stamen, and pistil.
Based on whether all of these four floral parts are present or anyone is absent, flowers are classified as either complete or incomplete.
A flower is called complete if all four floral organs are present in the same flower structure.
A commonly illustrated complete flower is that of the gumamela or China rose (Hibiscus rosa-sinensis).
An incomplete flower lacks any one or more of these parts.
The flowers of grass plants (family Gramineae or Poaceae) are mainly wind-pollinated and are incomplete, lacking both sepals and petals.
Relying on the wind to accomplish pollination, there is no need for these flowers to attract pollinators.