MOBPHOLOGY OF BEPKODUCTIVE OEGANS 117 



Chamomile ; or globular, as in the American Button-bush ; or 

 elliptical &c., by which a variety of forms is given to the different 

 capitula. 



The capitulum is the universal form of inflorescence in 

 plants of the natural orders Compositfe and Dipsaoese ; it also 

 occurs occasionally in some others. 



p. The Hypantliodium, — This form is shown in the Fig 

 (fig. 225). The receptacle, which is conical in the capitulum, is 

 in this case concave, forming a hollow chamber, along the walls 

 of which the flowers are arranged. The involucre which is so 

 prominent a feature of the capitulum is absent from the 

 hypanthodiuni. 



Fig. 221, 



Fiij. 224. Ciipitulum of Cutton T\ii^X\Q{(lnoponUim Aca/U/iitim). 



When, as in Dorstenia {fig. 226), the receptacle is nearly flat, 

 the margins only being slightly curved upwards, we have a form 

 intermediate between the capitulum and the hypanthodium. It 

 has been termed a coenanthium. 



Many of these types are found to merge into each other and 

 to render the identification of some forms difficult. Thus, the 

 only difference between the spike and the raceme being one of 

 length of pedicel, and this being a very variable part, it is 

 evident that the line of classification becomes somewhat arbi- 

 trary. The inflorescence may change its character as it grows 

 older, as has already been pointed out in the case of the corymb. 



