38 THE STRUCTURE OF FLOWERS. 



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

 flowered form of Hanunculus arpiatilis, with the small- 

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

 Eanunculus with. 3Iyosurus, in yfhich. 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 ^^ separated into whorls 

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

 of the two genera, which, have opposite leaves, comprising 

 the order Calycanthacece, Calycanthus illustrates an abrupt 

 change from opposite leaves to the ^\ aiTangement in the 

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

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

 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 bari'en ones of Calycanthus are here 

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

 sists of four distinct pentamerous whorls. 



