S8 THE STRUCTUEE OF FLOWERS. 



be seen by comparing the number of stamens in a large- 

 flowered form of Ranunculus aquatilis, with the small- 

 flowered B. hederaceus ; or one genus with an allied one, as 

 Ranunculus \Nii\i My osur us ^ in. yfhioh. the stamens are reduced, 

 often to one whorl of five only. 



Lastly, just as high spirals can be broken up into ternary 

 whorls, so can the arrangement 2t be separated into whorls 

 of a lower series, as of 13, 8, or 5 parts respectively. Thus, 

 of the two genera, whicb have opposite leaves, comprising 

 the order Calycanthacece, Calycanthus illustrates an abrupt 

 change from opposite leaves to the -/y arrangement in the 

 bract-like sepals of the flower ; but no distinction between 

 bracts, sepals, and petals can really be made. Chimonanthus, 

 however, would seem to be a more highly differentiated type, 

 in that, not only is the calyx distinguishable from the corolla, 

 but five exterior stamens constitute a distinct whorl by them- 

 selves, and the indefinite barren ones of Calycanthus are here 

 reduced to five ; so that, omitting the pistil, the flovrer con- 

 sists of four distinct pentamerous whorls. 



