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PLANT ORGANS AND ORGANISMS 
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Sepaline Position.- — As already noted the most simple and primi- 
tive position for the sepals in relation to the floral parts is hypogy- 
nous, in which the sepals are inserted directly into the enlarged floral 
axis (receptacle) below the petals, stamens and carpels. But in the 
more primitive herbaceous Rosacea, Leguminosa, etc., the floral 
axis forms a saucer-like transverse expansion which pushes out the 
sepals, petals and stamens on its edge. Thus originates the perigy- 
nous insertion of the sepals. In not a few higher Rosacea, Saxifraga- 
cea, Crassulacea, etc., the saucer-like floral axis becomes deepened 
and contracted into a cup-shaped structure (Cherry, Peach, Almond, 
Plum, etc.), and on the edge of this cup the sepals as well as the petals 
and stamens are inserted at different levels. Finally, in the Apple, 
Pear, Quince, etc., the greatly hollowed-out receptacle assumes a 
vase-shaped form and closes over the top of the ovary, at the same 
time lifting the sepals, petals, and stamens above the ovary. Here 
the sepals are epigynous. 
The Corolla. — The Corolla is the inner floral envelope, usually 
delicate in texture, and showing more or less brilliant colors and 
combinations of color. Its parts are called Petals, and when the 
calyx closely resembles the corolla in structure and coloring they 
are together called the Perianth. The purpose of these envelopes 
is to protect the reproductive organs within, and also to aid in the 
fertilization of the flower, as their bright colors, fragrance and sac- 
charine secretions serve to attract pollen-carrying insects. 
Forms of the Corolla and Perianth. — When the petals are not 
united with each other, the corolla is said to be Choripetalous, Apo- 
petalous or P oly petalous . When more or less united, they are Gamo- 
petalous, often called Synpetalous. 
When the distinct petals are four in number, and arranged in the 
form of a cross, the corolla is called Cruciform. Example: Mustard 
and other plants belonging to the order Cruciferae. 
The Papilionaceous corolla is so called because of a fancied resem- 
blance to a butterfly. The irregularity in this form is very striking, 
and the petals bear special names: the largest one is the vexillum, or 
standard; the two beneath it the ala, or wings; the two anterior, the 
carina or keel. Examples: Locust, Pea, and Clover. 
Orchidaceous flowers are of peculiar irregularity, combining calyx 
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