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 sep aline 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, 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- 

 ctce, 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 hollo wed-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- 



