BIOLOGY OF THE FLOWER 



173 



gonium destroys the symmetry of the flower. In the 

 previous examples the flower can be divided into more 

 than two similar halves. Such flowers are said to be 

 regular, or actinomorphic (Gr. aktis a ray, morphe = 

 shape). The Pelargonium, however, can be divided into 

 only two similar halves, and hence is said to be irregular or 

 zygomorphic (Gr. zygos = a yoke). 



The Garden Nasturtium should also be examined 

 (Fig. 118). Note the long spur, which is a hollow out- 

 growth of the floral axis and contains the honey. The 

 calyx, as well as the corolla, is coloured, and the fringes on 



Fig. 119. 1, Flower of Chervil ; 2, vertical section 

 of flower ; d, disk ; 0, inferior ovary. 



the three lower petals serve to keep rain out of the honey- 

 tube. Watch the stamens as they ripen, and note how 

 each in turn bends upwards in front of the entrance to the 

 tube and ripens so that it will be touched by a bee visiting 

 the flower. The}' then bend down out of the way, and 

 later the stigma assumes the position previously occupied 

 by the stamens, and is thus likely to become cross-pollinated. 

 The flower of the Chervil, or Beaked Parsley (Fig. 119), 

 shows several important differences. The flowers are small 

 and crowded together in a flat-topped inflorescence, called 

 a compound umbel (L. unibella = a sunshade). The calyx 

 consists of five minute sepals, and alternating with them 

 are five petals of different sizes ; the outer and anterior 

 one is the largest ; then follow two intermediate ones ; 



