INDEFINITE INFLORESCENCE. 



157 



spikelets, and these clusters are either set closely along a central axis 

 or rachis, or they are produced on a branched panicle. 



335. If the primary axis, in place of being elongated, is depressed 

 or flattened, it gives rise to other forms of indefinite inflorescence. 

 When the axis is so shortened that the secondary axes or peduncles 

 arise from a common point, and spread out like radii of nearly equal 

 length, each ending in a single flower, or dividing again in a similar 

 radiating manner, an Umbel is produced, as in figs. 240 and 241. In 

 fig. 240 the floral axes, a', a', a', end in simple umbels, o', o', </, and the 

 umbels are called stipitate or stalked; while in fig. 241 the primary 

 floral axis, a', is very short, and the secondary axes, a' a', come off" from 



Fig 238. Amentum or catkin of Hazel (Corylus Avellana), consisting of an axis or rachis 

 covered with bracts in the form of scales (squamce), each of which covers a male flower, the 

 stamens of which are seen projecting beyond the scale. The catkin falls off in a mass, 'separat- 

 ing from the branch by an articulation. 



Fig. 239. Spadix or succulent spike of Arum maculatum. 1 Exhibits the sagittate leaf, the 

 spatha or sheathing bract, 6, rolled round the spadix, the apex of which, a, is seen projecting. 

 2. Shows the spatha, 6, cut longitudinally, so as to display the spadix, a. f. Female flowers at 

 the base, m, Male flowers. On the spadix there are numerous abortive flowers indicated by 

 hair-like projections. 



Fig. -240. Several umbels, c/ o 1 <x </, of Aralia racemosa. a, General axis or the apex of the 

 branch terminated by a single umbel farther advanced than the rest a' a' a' a', Axes arising 

 from it, which are secondary as respects the general axis, a; each of them bears an umbel, and 

 as regards this inflorescence they are primary, a" a" a", Secondary axes, or the radii of the 

 umbel. 666, Bracts placed alternately on the general axis, d, Shows a double bud proceeding 

 from the axil of one of these bracts, and thus giving rise to two-stalked or stipitate umbels, 

 * e, Verticillate bracts, forming involucres at the base of the radii of the umbels. 



