118 



BIOLOGY 



REPRODUCTIVE ORGANS 



The organs which are designed for reproduction are widely 

 different in different groups of plants. Among the higher 

 plants this function is carried on by specially modified branches 

 known as flowers. Although the greatest variety is shown 

 among the flowers of different plants, when compared they 

 are readily seen to have the same general structure. The fol- 

 lowing description is not that of the flower of the castor bean, 

 or of any other plant, but an ideal description of a typical 

 flower, and in a general way applies to the flowers of all the 

 higher groups of plants. 



General Structure of a Flower. A flower is always borne 

 at the end of a stem; even although it appears to come from 



the side, when carefully exam- 

 ined it is found to be really 

 on the end of a short, unde- 

 veloped stem arising from the 

 side of the larger one. Indeed, 

 a flower is itself a short stem 

 bearing usually four rows of 

 leaves; Fig. 60. The stem of 

 the flower is called the pedun- 

 cle, p; at its top it is fre- 

 quently slightly enlarged to 

 bear the several rows of 

 leaves, this enlargement being 

 known as the receptacle, r. 

 The flower itself is composed 

 of four rows of leaves so 

 closely attached to each other 

 that they appear to arise at the same point of the stem; 

 careful study, however, shows that in all complete flowers 

 the four different kinds of leaves are produced one row above 

 the other. 



FlG. 60. DlAGEAM SHOWING THE 



PARTS OF AN IDEAL FLOWER 



a, the anther; 

 car, carpels; 

 p, peduncle; 

 pi, petal; 



r, receptacle; 

 s, sepals; 

 st, stamens. 



