38 



OEGANOGEAPHT AND GLOSSOLOGY. 



157. Dorstenia, 



156. Dandelion. 

 Naked receptacle. 



158. Fig. 

 Cut vertically. 



concave, bearing incomplete flowers inserted in pits witli ragged edges ; in the Fig 

 (fig. 158) the inflorescence is similar, but the receptacle is still more concave, inso- 



mucli that the male flowers, which are at the top of 

 the fig, answer in position to the lowest flowers of the 

 primary axis, and the small scales (bracts) at the 

 mouth represent an involucre, which in the normal 



state would gird 

 the base of the 

 common recepta- 

 cle, as in an or- 

 dinary head. 



It is obvious 

 that every indefi- 

 nite inflorescence 

 must be a modifi- 

 cation of the ra- 

 ceme ; thus the 

 corymb is a ra- 

 ceme with unequal 



secondary axes, reaching the same level; an umbel is a raceme whose primary 

 axis is undeveloped; the spike is a raceme whose secondary axes are undeve- 

 loped; the capitulum is a spike with the primary axis vertically thickened and 

 dilated. 



The difference between the raceme, corymb, umbel, spike, and head being simply 

 due to the amount of development of the primary and secondary axes, these terms 

 cannot be precisely limited, and intermediate terms are therefore frequently resorted to; 

 as spiked racemes and panicles, when the pedicels are very short ; a globose spike 

 approaches the head ; and an ovoid or spiked head approaches the spike. Amongst 

 Trefoils, capitulate, spiked, and umbelled flowers all occur. 



In the raceme, panicle, corymb, and spike, the pedicels flower from below up- 

 wards, i. e. the lowest flowers open first. In simple and compound umbels, the outer 

 flowers open first ; whence we may conclude that the umbel is a depressed raceme. 

 In the head, as in the depressed spike, the flowers really open from below up- 

 wards, but as the surface of the inflorescence in both these cases is nearly 

 horizontal, they appear to open from the circumference to the centre, and are 

 called centripetal, a term which is applied to every indefinite inflorescence, whether 

 the flowers open from below upwards, or from without inwards. 



Definite Inflorescences. — These are all included under the general terra cyme 

 (cyma), however much they may be branched ; they are, the definite- or cymose-raceme; 

 true corymb ; umbellate-cyme ; npicate-cyme, scorpioid cyme ; and contracted cyme, which 

 comprises the fancicle and the glomerule. 



1. In the definite- or cymose-raceme [Campanula, fig. 159), the flowering pedicels 

 are of nearly equal length, as in the raceme ; from which it differs in the primary 

 axis (a, a, a), terminating in a flower, which is necessarily the first to expand^ 



