Ch. VI, 11] MORPHOLOGY OF CLUSTERS 



335 



other facts of progressive consolidation and specialization 

 of parts above described, we see that the flower is by no 

 means closely bound by its former leaf and stem nature, but 

 has acquired in large measure its own morphological inde- 

 pendence. It is therefore in effect a morphological member 

 as well as a physiological organ of the plant. 



11. The Morphology and Ecology of Flower Clusters 



The conspicuousness of flowers, 

 especially of the smaller kinds, is 

 greatly augmented by their aggre- 

 gation into clusters. There is 

 more, however, in the subject than 

 this, for clusters often exhibit a 

 specific individuality, with distinc- 

 tive new characters of their own. 

 In wind-pollinated kinds, where 

 showiness has no functional value, 

 the clusters have apparently no 

 more than a structural significance, 

 as a convenience of development. 



Each flower originates in a bud, 

 representing morphologically a 

 spore-bearing determinate branch 

 (page 323) ; and flower buds, like 

 leaf buds, are usually either termi- 

 nal or axillary. Now every possible 

 gradation is found between a con- 

 dition in which solitary flowers are 

 scattered along stems in the axils 

 of green leaves and that in which 

 numerous flowers are massed densely 

 together with the leaves reduced to 

 insignificant bracts or wanting al- 

 iher. Where the solitary con- 

 dition ends and a cluster begins is 



I i .. 232. — Ercmurus 

 himulaicus, showing a rac- 

 emose spike of flowers. 

 (From Bailey.) 



