Tepal

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A tepal is a floral part of plants in the magnolia family, Magnoliaceae. It corresponds to the sepals and petals in the flowers of other plants, but unlike these, all tepals are of the same form, not being differentiated into the small, protective, not insect-attractive sepals that act as a protection for the developing petals, and the larger, insect-attracting petals.

A tepal in flowering plants (the angiosperms) is a unmodified sepal or petal that looks the same as a petal or the petals have been unmodified to look like sepals. Were the perianth is not differentiated into two distinctive segments, such as a calyx (made up of sepals) and a corolla (which is made up of petals). If one looks at a tulip flower one sees that it has no calyx or sepals, but they have been modified and look like petals and have fused at the base along with the petals to form one large showy six parted structure. In plants like lily the sepals are separated from the petals but look similar, thus all the showy parts are called tepals. Simplely, the word tepal is used to describe a flower that is composed of sepals and petals that can not be distinguished from each other - they appear the same.

Since its thought that the flowering plants evolved from a distant relative of the Magnolias (which were wind pollinated), one can see tepals place in the evolution of flowering plants. In the primitive magnolias all the parts of the flower are ether tepals or carpels or stamens. As flowers became more specialized to attract insects and birds (or bats) to pollinate the flowers, the tepals modified into large showy structures, and after more modifications and specialization some teplas became sepals and others became petals.

[edit] Merosity

Merosity is used to designate that a flower has whorls of floral parts in the perianth. It describes how many segments the whorl of petals or sepals or tepals have in a flower. Thus if a flower has five petals that look the same, then the flower is called 5-merous or has pentamery. Types of merosity, according to number of whorled segments in the perianth include:

• dimery (2)
• trimery (3)
• tetramery (4)
• pentamery (5)

These nouns for the different types of merosity are formed by a prefix derived from Ancient Greek (e.g. tetra- for four) and the suffixed root, -mery, which is derived from Greek meros meaning "part" thus four parted.

Additional reading:

'Botany A Brief Introduction To Plant Biology' 5th ed. Thomas L Rost; T Elliot Weier: Wiley & Sons 1979 ISBN 0-471-02114-8.

'Plant Systematics' Jones, Samuel B date: McGraw-Hill 1979 ISBN 0-07-032795-5.