358 



GENERAL BOTANY 



have arisen in 'the raceme type during the development of other 

 kinds of inflorescence. Thus, the spike is a racemelike inflores- 

 cence in which the numerous flow- 

 ers are sessile, without peduncles. 

 In the head a similar modification 

 in the peduncles has occurred, 

 together with a great shortening 

 and thickening of the axis of 

 inflorescence. In the umbel and 

 corymb the axis of inflorescence 

 is short and the peduncles are uni- 

 formly lengthened, so as to bring 

 the flowers at the same level, mak- 

 ing a flat-topped inflorescence. 

 Other types of inflorescence rep- 

 resent similar modifications from 

 the simple racemose type. 



Flowers. Flowers have various terms applied to them, based 



upon differences in form, structure, the presence or absence of 



the perianth or essential organs, and their spiral or cyclic plan. 



Cyclic and spiral are 



Petals' 

 -Sepals' 



cavity- 



^ 

 J nnflore 



Head 



Umbel 



Corymb 



FIG. 213. Diagram illustrating 

 various types of inflorescence 



Hypogynous 



Pwigynous 



terms used to desig- 

 nate the arrangement 

 of the parts of flowers 

 on the receptacle, or 

 axis. Since the flower, 

 as already indicated, 

 is a modified bud, or 

 branch, with the parts 

 corresponding to leaves, 

 we should expect the 

 same cyclic or spiral ar- 

 rangements of its floral 

 parts on the receptacle 

 as we have already found in the leaves on the stem axis. 



Epigynous 



l-JRcceptacle 

 Hypog'ynous Perigyndus Epigynous 



FIG. 214. Hypogynous, perigynous, and 



epigynous flowers 

 Diagrams above ; median sections of flower below 



In 



our discussion of the flower of the marigold it was indicated 

 that such flowers, with spirally arranged parts, represented the 



