298 



FLOWERS 



amples ; their inflorescences go on flowering throughout the 

 season. 



If the youngest flowers are at the sides or at the bottom 

 of the inflorescence, the older ones being at the center or 

 top, it is of the determinate type. The 

 extent of its flower production appears 

 to be determined beforehand. The grow- 

 ing tip ends with the oldest flowers. The 

 inflorescences of geranium are determi- 

 nate. 



When it comes to describing inflores- 

 cences, certain terms not used before are 

 needed. You have noted that a flower 

 is composed of the end of a stem and of 

 certain modified leaves which arise from 

 it. It arises usually, as any other branch 

 arises, from the axil of a leaf. In in- 

 florescences those leaves from whose axils 

 the flower branches arise are usually very 

 much smaller than ordinary leaves. 

 They are called bracts. (See Figure 118.) 

 Any small, leaf-Hke organ found in an in- 

 florescence, but not a part of a flower, is 

 properly called a bract. You have noted 

 those green structures which cover dan- 

 dehon heads when they are closed. 

 These structures are bracts. They form what is called the 

 involucre. (See Figure 124.) The heads of all Compositce 

 are surrounded by involucres which, in function, correspond 

 to the calices of other kinds of flowers. The stem which 

 bears a single flower is called the pedicel; its outer end is 

 the receptacle. Evidently the flowers of Composite do not 



Fig. 118. — A raceme 

 of Veronica-. Note 

 the pedicels, each 

 one arising from the 

 axil of a iracl. 



