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FLOWER STRUCTURE

Flowers consist of a maximum of four whorls of structures, some of which are modified leaves.  In most flowers, the outermost whorl consists of sepals which are typically green and leaflike and may protect the flower before it opens.  Inside this is a whorl of modified leaves known as petals which are often large and brightly colored.  Inside the ring of petals are the male structures known as stamens and the female structures known as pistils.   The stamens produce the male reproductive cells (either sperm or the cells which become sperm upon division) wrapped in a nitrogenous coat forming pollen grains.  When pollen grains land on the pistil, they grow long tubes to reach the ova and fertilize them to form the embryos of new plants.  In many flowers, the sex organs which are hidden within a flower while in other flowers these are quite exposed, such as in this smooth azalea (the stamens are white and the pistils are red). 

AZALEA  

     Not all of these four parts of a flower are present in all flowers and great variations of the sepals and petals are known.  For example, a flower may lack either male or female structures and be a single sex flower rather than a hermaphroditic one.  A single plant may possess flowers of only one gender, a mix of male and female flowers, hermaphroditic flowers, or some combination of these.  Some flowering plants change their gender over the course of their lives.  The sepals in some flowers are brightly colored.  The number and arrangement of the petals can vary greatly.

     Flower petals vary in structure.  Some are irregular in their form, such as columbine,

COLUMBINE

iris,

iris

mad dog skullcap,

mad dog skullcap

and butter and eggs.

butter and eggs

Some flowers have two regular parts, such as cypress spurge.spurge

Some flowers have three regular parts such as spiderwort,

spiderwort

and this water lily.

water lily

Some flowers have four regular parts such as garlic mustard,

garlic mustard

and partridgeberry.

partridgeberry

Some flowers have five regular parts such as buttercups,

buttercup

Deptford pinks,

Deptford pinks

and fringed loosestrife.

fringed loosestrife

Some flowers have six regular parts such as star of Bethlehem

,

star of Bethlehem

and blue eyed grass.

blue eyed grass

Some flowers have seven regular parts such as starflower.

starflower

A large number of flowers have many regular parts such as asters,

aster

black-eyed susan,

woodland sunflower,

woodland sunflower

Cynthia,

Cynthia

fleabane,

fleabane

and round-leaved ragwort.

round-leaved ragwort