i6o 



PLANT BIOLOGY 



Dense centrifugal clusters are 

 usually flattish on top because of 

 the cessation of growth in the 

 main or central axis. These com- 

 pact flower-clusters are known 

 as cymes. Centrifugal clusters 

 are sometimes said to be cymose 

 in mode. Apples, pears (Fig. 

 220), and elders bear flowers in 

 cymes. Some cyme-forms are 

 like umbels in general appear- 

 ance. A head-like cymose clus- 

 ter is a glomerule ; it blooms from 

 the top downwards rather than 

 from the base upwards. 



Mixed Clusters. Often the 



cluster is mixed, being determi- 

 FIG. 219. DETERMINATE OR 



CYMOSE ARRANGEMENT. nate in one part and indeterminate 



Wild geranium. in another part Q f the same dus _ 



ter. The main cluster may be indeterminate, but the 

 branches determinate. The cluster has the appearance of 

 a panicle, and is usually so called, but it is really a thyrse. 

 Lilac is a familiar example of a 

 thyrse. In some cases the main 

 cluster is determinate and the 

 branches are indeterminate, as in 

 hydrangea and elder. 



Inflorescence. The mode or 

 method of flower arrangement is 

 known as the inflorescence. That 

 is, the inflorescence is cymose, co- 

 rymbose, paniculate, spicate, solitary, determinate, inde- 

 terminate. By custom, however, the word " inflorescence " 



FIG. 220. CYME OF PEAR. 

 Often imperfect. 



