70 ARRANGEMENT OF FLORAL LEAVES 



there should be an equal number of floral leaves in each 

 whorl, and the successive whorls should alternate. Often we 

 are assisted in comprehending the apparent exceptions to these 

 rules by observing the structure of flowers belonging to plants 

 closely related, and therefore included in the same family (see 

 Foxglove-family, page 157). And again we know that a foliage- 

 leaf commences as a single little lump on the surface of the 

 stem. A separate floral leaf arises in the same manner. If, 

 therefore, we see five lumps grow out to form the commence- 

 ment of the androecium of a flower, and they alternate with 

 five outgrowths which are the beginnings of the petals, we 

 can assume that the androecium is constituted of five stamens, 

 however the stamens may cohere or branch subsequently. 



Symmetry of Cyclic Flowers. — If we compare the flower 

 of a Geranium or Hyacinth with that of a Pea (figs. 96, 97) 



98 



99 



Fig. 98. — A regular actinomorphic cyclic flower on an axis {ax) in the axil 

 of a bract (^r) : ^r=lateral prophylls; a.j = anterior sepal ; /=posterior petal. 

 The dotted line down the axis and over the flower is median. 



Fig. 99. — The same flower showing the various floral leaves. 



or Clover, we note that, in the case of the first two plants, 

 all the parts are regular, and are arranged in such a manner 

 that the flower can be divided down the centre into two equal 



