134 



Elementary Botany 



although fertilised by insects, bear fruit. They are followed in 

 the summer by small inconspicuous apetalous flowers, where the 

 stamens and pistil are enclosed in a calyx which does not open. 

 The result is, the flowers are fertilised by their own stamens. 

 Such flowers are said to be eleistogamous. Besides this there are 

 other examples where self-fertilisation is specially provided for. 



RELATION OF FLOWER TO OTHER PARTS OF THE PLANT. 



The parts of the flower must be looked upon as modified 

 foliar organs. This is pretty evident in the calyx and corolla, 

 but not so well seen at first in the stamens. We have proof, 

 however, in the facts, ist, of the tendency in double flowers to 

 form petals instead of stamens ; and 2nd, the gradual transition 

 from petals to stamens as seen in the white ^Vater-lily, or 

 Rosa centifolia (fig. 255). 



Fig. 255. -- Stages of transition between the petals and stamens of 

 Rosa centifolia^ 



In some cases the filament appears to represent the petiole, 

 the connective the midrib, and the anther the blade, when the 

 pollen would represent the general internal tissue of the leaf 

 In other cases the filament appears to be the leaf-blade, and 

 the anthers and pollen appendages upon it. 



We must regard the carpels as leaves (carpellary leaves), 

 either folded over so that their edges meet, when the dorsal 

 suture marks the midrib, and the ventral the margin of the 

 leaves, or, in a unilocular polycarpellary pistil, the carpellary 

 leaves unite by their margins. The placenta is developed on 

 the margin of the carpellary leaves, or in the free central placen- 

 tation on the prolongation of the stem. The ovules are ap- 

 pendages of the carpellary leaves, or, in the case of the free 

 central placentation, buds upon the prolonged axis, 



