212 



THE INFLORESCENCE. 



386. An Umbel (Fipj. 310) differs from a corymb only in having 

 all the pedicels arising from the same apparent point, so as to resem- 

 ble the rays of an umbrella; — the general peduncle, in this case, 

 bearing several flowers without any perceptible elongation of the 



axis of infloresence. The Primrose and the Milkweed afford 



familiar examples of the simple umbel. 



387. A corymb being evidently the same as a raceme with a 

 short main axis, and an umbel the same 

 as a corymb with a still shorter axis, 

 it is evident that the outer flowers of 

 an umbel or corymb correspond to the 

 lowermost in the raceme, and that these 

 will first expand, the blossoming pro- 

 ceeding regularly from the base to the 

 apex, or (which is the same thing) from 

 the circumference to the centre. This 

 mode of development uniformly takes 

 place when the flowers arise from axil- 

 lary buds ; on which account the indefi- 

 nite mode of inflorescence is also called 

 the centripetal. 



388. In all the foregoing cases, the 

 flowers are raised on stalks, or pedicels. 

 "When these are wanting, or so short as 

 not to be apparent, a Spike or Head is 

 produced. 

 389. A Spike is the same. as the raceme, except that the flowers 



are sessile ; as in the Plantain (Fig. 311) and Mullein. It is an in- 



FIG. 318. A raceme. 309. A corymb. 310. An umbel. 



FIG. 311. Young spike of Plautago major 312. Catkin of White Birch. 



