224 



BOTANY OF THE LIVING PLANT 



flowers which bloom during a prolonged period, instead of simul- 

 taneously. These are among the biological advantages gained by 

 complicated inflorescences. 



The characteristic features which inflorescences show depend upon four 

 main factors : (i) the arrangement of the leaves (bracts) in the axils of which 

 the branches arise ; (ii) the proportion of intercalary growth of the several 

 axes ; (iii) the number of flower-buds produced ; and (iv) the succession 

 in which the buds mature. Of these the most important is the last, and 

 inflorescences may be classed according to its consequences as Definite or 

 Indefinite. If a distal flower blooms first that will stop the apical growth 



I 

 -\ / 



i ^ 



\ 



V 



\ 



or 



\ 



T 



I 



y 



;D 



FIG. 170. 



Diagrams of common types of Inflorescence. A, B, definite ; C, D, E, indefinite. 

 The numbers indicate the succession of the flowers. See text. 



of the main axis, and all further flowers must be borne on lateral axes. Such 

 inflorescences are termed Definite, or Cymose (Fig. 170, A, B). They com- 

 monly develop sympodially, that is, the lateral axes grow so as to overtop 

 the main axis. But if the buds on lateral branches bloom first, the apex 

 may still continue to grow, and to form additional bracts and flowering buds. 

 Such inflorescences are called Indefinite, or Racemose (Fig. 170, C, D, E). 

 They usually work out along monopodial lines, that is, the main axis 

 remains dominant, and the lateral axes are accessory. 



The simplest Cymose or Definite inflorescence is illustrated by the Tulip, 

 with its solitary flower terminal on the peduncle, or main flower-stalk. But 

 in the bulb below, an axillary bud matures during the season, which will 

 repeat the flowering axis in the next year, and so on. The Tulip is then a 

 definite inflorescence, with an interval of a year between its flowers. Its 

 branch-system is sympodial, each succeeding axis overtopping its predecessor. 





