222 



THE INFLORESCENCE. 



more or less elongated inflorescence which is irregularly branched 

 twice, thrice, or a greater number of times. 



400. A Thyrsus is merely a compact panicle of a pyramidal, oval, 

 or oblong outline ; such as the cluster of flowers of the Lilac and 

 Horsechestnut, a bunch of grapes, &c. 



401. Definite or Determinate Inflorescence, In this class, the flow- 

 ers all represent tecwiinal buds (380). The primary axis is direct- 

 ly terminated by a single flower-bud, as in Fig. 249, and its growth 

 is of course arrested, as it is now incapable of any further elonga- 

 tion. In this way we have a solitary terminal flower. Further 

 growth can take place only by the development of secondary axes 

 from axillary buds. These may develope at once as peduncles, or 

 as leafy branches ; but they are in either case arrested, after more 

 or less elongation, by a flower-bud, just as the primary axis was 

 (Fig. 250). If further development ensues, it is by the production 

 of branches of the third order, from the axils of leaves or bracts on 

 the branches of the second order (Fig. 251) ; and so on. Hence 

 this mode of inflorescence is said to be definite or determinate, in 

 contradistinction to the indeterminate mode, already treated of 

 (382, &c.), where the primary or leading axes elongate indefi- 

 nitely, or merely cease to grow from the failure of nourishment, or 

 some other extrinsic cause. The most common and most regular 

 cases of determinate inflorescence occur in opposite-leaved plants, 

 for obvious reasons ; and such are accordingly chosen for the sub- 

 joined illustrations. But the Rose, Potentilla, and Buttercup fur- 

 nish* familiar examples of the kind in alternate-leaved plants. 



402, The determinate mode of inflorescence assumes forms 

 which closely imitate the various forms of the indeterminate kind, 

 already described, with which they have been confounded, and 



FIG. 249-251. Diagrams of regular forms of determinate or centrifugal inflorescence. 



