THE FLOWER 



89 



The leaf-like character of the ordinary sepal is very generally 

 recognized. The petals are rarely green, but otherwise there is 

 no good reason for believing that their origin is materially dif- 

 ferent from the sepals. In many flowers the petals are of some 

 color other than green, and in many cases it is difiicult to dis- 

 tinguish the calyx from the corolla. The stamens and pistils 

 appear to be very different from, the leaves, but it is nothing 

 uncommon to find specimens in which these organs are petal- or 

 leaf-like. In fact, the white water lily shows a gradual transi- 

 tion from stamens to petals and from petals to sepals. Many of 

 our so-called double flowers, such as the roses and carnations, are 

 ca^ in which the stamens have reverted into petals. 



Inflorescence (Fig. 68). — The arrangement of the flowers on 

 the stem is called the inflorescence. It may be expressed in dia- 

 gram as follows : 



Inflorescence 



Solitary 



[Axillary 

 [Terminal 



CoBymbose 

 (Indeterminate) 



Clustered 



Raceme 



Panicle 



Thyrsus 



Cori ■ 



Uml 



Spike 



Head 



Spadix 



Catkin 



yrsusv, 



Simple 

 Compound 



Cymose 

 (Determinate) 



rCyme 



\ Helicoid cyme 



[Scorpioid cyme 



Solitary, of course, refers to lone flowers, as compared with 

 clustered or grouped flowers. The former are borne on short 

 shoots in the axils of the ordinary leaves (i.e., axillary), or at the 

 tips of the main shoots (i.e., termvnal). 



In the clustered inflorescence the flowers are grouped on an 

 axis which may be long or short. In the corymbose or irvdeter- 



