ITS IRREGULARITY. 



261 



separate names ; the upper one, which is usually most conspicu- 

 ous, being termed the vexillwn, standard, or banner (Fig. 318, a) ; 

 the two lateral (Z>) are called wings (ala), and the two lower (c), 

 which are usually somewhat united along their anterior edges, and 



more or less boat-shaped (Fig. 319), together form the keel (cari- 

 rca). The sepals, which are coalescent below into a cup, are also 

 of unequal size or somewhat unequally united. But here are all 

 the parts of a symmetrical pentamerous calyx and corolla, only 

 they are irregular on account of their unequal size, shape, or un- 

 ion. There is a tendency to become regular, however, in some 

 flowers of the same tribe ; this is slightly observable in Baptisia 

 (Fig. 321), but is more manifest in Cercis (the Red-bud or Judas- 

 tree), and most of all in Cassia ; where the five petals are separate, 

 spreading, and almost alike in size and form. The irregularity of 

 papilionaceous flowers likewise affects the stamens, which, although 

 of symmetrical number, viz. ten, or two circles, are in most cases 

 unequally diadelphous (462), nine of them being united by the cohe- 

 sion of their filaments for the greater part of their length, while the 



FIG. 317. A flowering branch of Lathyrus myrtifolius. 318. The corolla displayed : a, the 

 vexilhim or standard; b, the alee or wings; c, the two petals of the carina or keel. 319. The 

 keel-petals in their natural situation. 320. The stamens and pistil, enlarged ; the sheath of 

 filaments partly turned back. 



