CHAPTER XI. 



THE rOEMS OF FLOEAL OKGANS. 



The Form of the Perianth — General Observations. — It 

 requires but a most cursory observation of flowers to notice 

 how great is the variability in the forms of all their organs ; 

 and the questions now before ns are, how these morphological 

 characters are correlated to the one process of pollination in 

 order to secure the fertilisation of the flower, and how this 

 infinite diversity of form has arisen. 



Most important differences in this respect follow from the 

 fact of flowers being regular or irregular, and, when adapted 

 to insects, according as the honey is easily accessible or not. 

 Regular * flowers when borne singly are almost always 

 tei-minal ; t and when they are arranged in racemes, etc., 

 they either stand out erect at the ends of their pedicels so as 

 to be readily approached at any point of their circumference, 

 as in the Wallflower, or else they are pendulous ; under which 

 conditions, as a rule, no particular part is favoured by the 



• It is nsnal to speak of a flower as being regular or irregolar ; but 

 the term shonld be, strictly speaking, confined to one whorl at a time ; 

 thongh when the corolla is irregular, the calyx and stamens are asoally 

 somewhat irregular as well. 



t The central and terminal flowers of many plants which elsewhere 

 bear irregnlarflowers are often regular, as in Horse-chestnut.PeSor^omuTn, 

 several of the Scrophidarinem, as Snapdragon, Lmaria, Pentstemon, etc. 



