156 



INDEFINITE INFLORESCENCE. 



a thyrsus is produced, as in Like. If in a raceme the lower flower- 

 stalks are elongated, and come to nearly a level with the upper, a 

 corymb is formed, which may be simple, as in fig. 235, where the pri- 



mary axis, a', divides into secondary axes, a" a", which end in single 

 flowers; or compound, as in fig. 236, where the secondary axes again 

 subdivide. 



334. If the peduncles or secondary axes are very short 

 or awanting, so that the flowers are sessile, a spike is pro- 

 duced, as in Plantago and Verbena officinalis (fig. 237). 

 The spike sometimes bears unisexual flowers, usually stami- 

 niferous, the whole falling off by an articulation, as in Wil- 

 low or Hazel (fig. 238), and then it is called an amentum 

 or catkin; at other tunes it becomes succulent, bearing 

 numerous flowers surrounded by a sheathing bract or spatha, 

 and then it constitutes a spadix, which may be simple, as in 

 Arum maculatum (fig. 239), or branching, as in Palms. 

 A spike bearing female flowers only, and covered with 

 C^ scales, is either a strobilus, as in the Hop; or a cone, as in 

 Y the Fir (fig. 201). In grasses, there are usually numerous 

 037 sessile flowers arranged in small spikes, called Locustce or 



Fig. 235. Corymb of Cerasus Mahaleb, produced in the axil of a leaf which has fallen, and ter- 

 minating an abortive branch, at the base of which are modified leaves in the form of scales, f. 

 a 1 . Primary axis, or peduncle, or rachis, producing alternate bracts, 6 6, from the axil of which 

 secondary axes or pedicels, a" a", arise, each bearing a single flower. The evolution or expansion 

 of the flowers is centripetal 



Fig. 236. Compound or branching corymb of Pyrus torminalis. of, Primary axis. a" a", 

 Secondary axes, a!" a'". Tertiary axes or pedicels bearing the flowers directly. 666, Bracts. 



Fig. 237. Spike of Verbena offlcinalis, showing sessile flowers on a common rachis; the in- 

 florescence indeterminate, and the evolution of the flower centripetal. The flowers at the lower 

 part of the spike have passed into fruit, those towards the middle are in full bloom, and those at 

 the top are only in bud. 



