• Sepals form a protective layer over the developing flower.flower bud image by Dat from Fotolia.com
  
  The calyx is a protective layer of vegetable matter that forms around developing flowers. It is characterized by tough leaf-like structures that begin growing bundled in a teardrop shape and gradually open to reveal the parts of the flower developing within. When a young flower is enclosed within the calyx, all of its parts can be said to be a part of the calyx, but as the petals, carpel and stamen emerge, only the leaves continue to be identified as the calyx. These leaves, called sepals, can take a variety of forms.
  
  

Regular Sepals

• In many flowers, the calyx is made of sepals. These are leaf-like structures which protect the flower's other parts while it is developing. The number of sepals in the calyx is typically consistent with the number of petals on the flower. They are arranged so that they alternate with the petals. These sepals create a regular, symmetric pattern as they radiate from the tip of the stem, beneath the corolla of the flower.
  
  

Fused Sepals

• In some species, sepals naturally develop fused together along part or all of their edges. In other species where regular sepals normally occur, environmental factors can cause the sepals to undergo either partial or full fusion. The result is a calyx comprised of one fused layer or skin, which is torn open as the flower emerges.
  
  

Asymmetric Sepals

• In the case of fused sepals, the calyx is almost always torn into an irregular and asymmetric arrangement as the flower emerges. Otherwise regular sepals may also become irregular due to the affects of a harsh environment or tampering by parasites. Sepals do not normally develop asymmetrically under ideal growing conditions.
  
  

Tepals

• In some species, such as lilies, the sepals of the calyx and petals of the corolla of the flower are indistinct from each other. In these flowers, the petals themselves form the calyx during early development and are classified as tepals. Because there are no separate parts to open or tear when the flower opens, tepals are natural symmetric and unfused.