34 



PART I. THE MORPHOLOGY OF PLANTS. 



[. 



worts (e.g. Marchantiaceae) ; in the leaves of some Ferns ; in the roots of 

 Lycopodium and Isoetes ; in the stem of some Lycopodiums (L. alpinum, 

 dichotoma). In the Phanerogams it only occurs in inflorescences and flowers. 



It will be observed that dichotomous branching necessarily 

 involves the limitation of growth of the branching member. 



2. In lateral branching, the new members are developed 

 laterally from the parent member. Two forms may be distin- 

 guished, the monopodial and the cymose. 



a. Monopodial branching. The characteristic feature of a mono- 

 podial branch-system is the presence of a main axis (monopo- 

 dium), formed by the continued elongation of the branching 



ff S 



FIG. 19. Cymose branch-systems represented diagrammatically. When the branches 

 are regarded as all lying in one plane (that of the paper), A and B represent the Rhipi- 

 dium, and D the Drepanium. When the branches are regarded as lying in various planes, 

 A and B represent the scorpioid (cincinnal) cyme, and D the helicoid (bostrychoid) cyme ; 

 C, the dichasial cyme, the branches being regarded as lying in various planes. 



member, bearing a number of less highly developed lateral axes. 

 This is due either to the greater rapidity, or longer duration, of 

 the growth of the branching member as compared with that of the 

 lateral members. 



A good example of the former case is afforded by Firs. Here 

 both the primary shoot and the main lateral shoots have un- 

 limited growth ; but the former grows more rapidly than the latter, 

 and so constitutes a main axis. 



A good example of the latter is afforded by racemose inflores- 

 cences. Here the growth of each of the members of the branch- 



