36 THE STEUCTUKE OF FLOWERS. 



ceatral floret of the cyme has often a higher number than that 

 of the lateral ones ; so that if they be 6-merous, the central 

 flower -will be 7-merous. Agapanthus, amongst Monocoty- 

 ledons, is another instance, its flowers ranging from 6 to 8 in 

 the number of parts in the whorls. 



OcTAMEEOUS Whoels. — A whorl of eight parts is not 

 common ; but it .appears in GMora and in the corolla of Dryas 

 oetopetala, in which it may be a cycle of the f phyllotaxis. 

 In other oases it is a combination of two whorls, which, as a 

 rule, can be easily distinguished as the stamens in the Ona- 

 gracece, or it may be due to symmetrical change. 



Enneameeotjs "Whorls. — The number 9, like 6, 7, and 11, 

 corresponds to no cycle of any one of the usual forms of leaf- 

 arrangement, and is proportionately rare. It may occur as a 

 combination of three cycles of three each, and perhaps this 

 wiU account for it when it occurs in Trientalis, and the 

 androecium of Mercurialis. The stamens of ButoTnus are 

 also nine in number. 



Decameeous Whoels. — The number 10 never occurs 

 except as the union of two whorls of five in each, as in the 

 androecium of LeguminoscB. 



Endecameeous Whoels. — Like 7, the number 11 might 

 occur if the series J, i, f , -^, etc., was as frequently repre- 

 sented as ^, I, I, f, etc., when "sevens " would be as abun- 

 dant as " fives " are now. I do not know of a case where it 

 could reasonably be referred to such an origin. "When it 

 does occur, as in CupJiea, it is clearly due to an arrest of one 

 stamen through insect agency. Brownea is said also to have 

 sometimes 11 stamens ; if so, this would undoubtedly be due 

 to numerical increase. 



DoDECAMEEOUS "Whoels.— The number 12 closely verges 

 on the "indefinite," which simply means a more or less 

 numerous series of cycles of the same kind. Neverthe- 



