VEGETATIVE AND SEXUAL REPRODUCTION 161 



apparatus is necessary in order to make sure that the male 

 gametes will reach the female gametes and fertilize them. 



To insure this union of the sex cells the flower has been 

 evolved, with its complicated apparatus for attracting insects and 

 for holding the pollen brought to the stigma by wind or insects. 



THE FLOWER AND ITS PARTS 



The flower is the reproductive apparatus of the higher plants, 

 designed to insure sexual union of the gametes and the produc- 

 tion of embryos in the seed. The early history of the flower 

 shows that it is a modified shoot or bud in which the parts have 

 been changed to meet the needs of a highly organized repro- 

 ductive apparatus. No attempt will be made here to trace the 

 steps in the development of the flower or to give its manifold 

 variations in the different orders of plants. We shall rather 

 study the parts of a typical flower and then endeavor to trace 

 the processes of pollination and fertilization. 



The simple flower of the mandrake (Fig. 84) will be used 

 to illustrate the following general discussion of the parts of a 

 typical flower and its fruit. See also the flowers of the marigold 

 and the buttercup in Part III. 



Peduncle and receptacle. Most flowers are borne on a slender 

 stalk, or peduncle, w r hich is enlarged at its apex to form the 

 receptacle. The floral parts have their origin on this receptacle, 

 which corresponds to the apex of the floral branch. 



The perianth. The perianth is usually composed of two dis- 

 tinct parts : the calyx, composed of separate leaflike parts called 

 sepals, and the corolla, composed of individual parts called petals. 

 The petals are frequently highly colored and constitute the 

 showy part of common cultivated and wild flowers. The calyx 

 springs from the receptacle just below the corolla ; in the man- 

 drake it is composed of six sepals, which fall off as soon as the 

 flower opens from the. bud. In addition to its function as a flag 

 apparatus to attract insects the perianth serves as a protective 

 envelope for the essential organs of the flower, the stamens and 

 the pistil. In the bud stage these organs are completely inclosed 



