INFLORESCENCE. 



35 



fig. 135). In the Stock and many allied plants, the inflorescence is at first a corymb, 

 but changes to a raceme as the primary axis lengthens. 



3. In the umbel (umbella) the secondary axes are equal in length, and starting from 



the same point, flower at the same 



height, diverging like the rays of a 



parasol ; it is a raceme of which 



the primary axis is reduced almost 



to a point. The umbel is simple 



(sertulum), when the secondary axes 



flower (Cherry, fig. 136) ; it is com- 



pound, when these bear umbellately 



arranged tertiary axes, called 



partial umbels (umbellulce, Fennel, 



138. Carrot. Umbels with in.olucre ; 

 umbellate with inyolucels. 



%' W> Carrot > 

 Parsley, fig. 139). 



138 5 



139. JEthusa. 

 Umbel without involucre ; 

 umbelluTce with involucels. 



The bracts, which in most racemes spring, like the pedicels, from different heights, 

 in many umbelliferous plants rise on a level, like the secondary and tertiary axes, 

 and form a whorl. The name 

 involucre (involucrum) is given to 

 the bracts at the base of the umbel 



140. Plantain. 

 Simple spike. 



141. Vervain. 

 Simple spike. 



142. Wheat. 

 Compound spike. 



143. Oat. Panicle of spikelets. 



(Carrot, fig. 138), and that of involucel or partial involucre (involucellum) to the 



D 2 



