VII] CYCLIC AND ACYCLIC FLOWER 57 



the first place, to the progressive shortening of the floral 

 axis and internodes : the whole structure is, so to speak, 

 longitudinally condensed. 



It is the custom to speak of flowers as acyclic when 

 their parts are all spirally arranged, and as cyclic where 

 they are in distinct whorls : those cases where the stamens 

 and carpels are spirally arranged, but the remaining parts 

 are in whorls, are termed hemicyclic. From what has been 

 said it will be understood that acyclic flowers are the rarest, 

 and that hemicyclic flowers are not common, both being 

 confined to a few existing groups only : the vast majority 

 of flowers are cyclic. No doubt this is due to the gradual 

 extermination of the more primitive spiral arrangement 

 as the cyclic flowers adapted themselves more and more 

 perfectly to the necessities of their environment and 

 functions. 



This condensation of the floral axis has taken place in 

 very different degrees in various flowers, moreover, for 

 although the rule is that the insertion of the floral parts 

 are so crowded condensed as it were that no inter- 

 nodes can be discerned, distinct and even long internodes 

 are in some rare cases observable in the flower, quite 

 apart from those common beneath it : the latter, for 

 instance, occur between the bracts and the flower in 

 Anemone, Herb-Paris, &c. Such internodes in the floral 

 region are also to be seen in Lychnis viscaria between 

 the calyx and corolla ; in Gynandropsis pentaphylla 

 between the corolla and androecium, and again between 

 the andrcecium and gynoecium ; in Passion-flowers and in 

 some Sterculiacece between the corolla and androscium ; 

 while in the North American Crucifers Warea and 

 Stanleya and some allied plants the gynoecium is always 

 separated by a long stalk-like internode from the 

 andrcecium. 



