PLANT ORGANS AND ORGANISMS 
185 
family. Thus in Potentilla, Fragaria, Geum, etc., in addition to the 
normal calyx of five sepals, there is a supplementary epicalyx also of 
five parts. The five lobes of the epicalyx may be as large or larger 
than the sepals or smaller up to the disappearing point. Upon 
examining a few flowers of Potentilla or Fragaria , it will be observed 
that not infrequently one, sometimes two lobes of the epicalyx are 
bifid, or deeply cleft, or separated completely into two parts. The 
explanation is that the five sepals, after evolving in the flower bud, 
form at their bases two lateral swellings or sepaline stipules, which, as 
they grow, fuse in adjacent pairs, one stipule of one sepal joining 
with the adjacent stipule of another sepal to form five lobes. 
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 Rosacece, Leguminosce , 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 Rosacece, Saxifraga- 
cece, Crassulacece , 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 texttire, 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- 
