8o THE FLOWER 



very short internodes is, however, apparent from a study of its 

 origin and position upon the plant and also from an examina- 

 tion of abnormal or monstrous flowers which occasionally occur. 



A flower always occupies the position of a shoot; it arises 

 either at the apex of a stem or in the axil of a leaf. Its receptacle, 

 which normally ceases growth in length at an early period, occa- 

 sionally grows on through the centre of the flower and develops 

 into an ordinary leafy vegetative shoot. 



The sepals, petals, stamens and carpels occupy the position of 

 leaves upon the receptacle or axis of the flower ; they are lateral 

 appendages of the receptacle and are termed yfora/ leaves. More- 

 over, the leaf-like character of the sepals and petals is generally 

 obvious, and in so-called ' double flowers ' some or all of the 

 stamens and carpels assume the appearance of petals. 



4. Arrangement, Symmetry and Number of Floral Leaves. — 

 When the whole of the floral leaves are arranged in whorls, the 

 flower is said to be cydt'c : if they are inserted in a spiral line on 

 the receptacle, the flower is described as acyclic. The term hemi- 

 cyclic is applied to those flowers which like the buttercup have 

 some of their floral leaves in whorls and others in spirals. 



Generally the successive whorls alternate with each other : the 

 petals for example are not opposite to the sepals, but occupy 

 the spaces between the latter; the stamens alternate with the 

 petals and the carpels with the stamens. 



Very often the individual members of each separate whorl in 

 a cyclic flower are all alike in shape and size ; such a flower is 

 regular, while those in which this is not the case, as in the pea 

 and violet, where some of the petals are larger than the rest, the 

 flower is irregular. 



All those flowers which can be divided into two equal and similar 

 halves by a plane passing through the axis of the receptacle are 

 symmetrical. Usually regular flowers can be divided into two 

 halves by planes passing through the axis in several different 

 directions : they are designated actinomorphic flowers, examples 



