The flower tube, also known as the hypanthium, is an important part of the flower structure. It is a cup-like structure that surrounds the ovary of the flower and can be either tightly or loosely fused to the ovary walls. The rim of the hypanthium is where the calyx lobes (free sepals), petals, and either one or two whorls of stamens or numerous stamens are located.
The hypanthium is an important structure for the flower as it helps to protect the ovary and the developing fruit. It also helps to support the petals and sepals, which are important for attracting pollinators. In some flowers, the hypanthium also acts as a nectar guide, directing pollinators to the nectar-producing parts of the flower.
The hypanthium can vary in size and shape depending on the species of flower. Some flowers have a shallow hypanthium, while others have a deep one. Some flowers have a hypanthium that is fused to the ovary walls, while others have a hypanthium that is loosely attached.
The hypanthium is an important structure for the flower and plays an important role in the pollination process. It helps to protect the ovary and the developing fruit, and also helps to support the petals and sepals. Understanding the structure and function of the hypanthium can help us to better understand the pollination process and the evolution of flowers.