88 



THE FLOWEKING PLANT. 



Fig. 41. — Petal 

 Pink. I. limb 

 claw. 



shaped (fig. 42). 



growth at the junction of the two, which is termed a ligule from 

 its resemblance as regards position to the structure of that name 

 in grasses. The ligules are collectively called the corona. One 

 or more petals of the polypetalous corolla may be saccate or 

 spurred. In the pansy and violet the lower petal is produced 



into a large spur (fig. 51). 

 Larkspur and monkshood 

 (p. 85) have two spurred 

 petals, while all five petals 

 have conspicuous spurs in 

 the closely allied colum- 

 bine, where the corolla is 

 regular. A very common 

 and striking form of irre- 

 gular corolla with free 

 petals is seen in gorse, pea, 

 bean, wistaria, clover, &c. 

 It has been termed papi- 

 lionaceous or butterfly- 

 The odd posterior petal is here larger than the 

 est, and being somewhat upright, is known as the standard 

 (vexillum). In front of this come a fairly large pair of petals, 

 the wings (alee), which overlap a third smaller pair that are 

 united into a boat-shaped structure, the keel (carina), enclosing 

 the stamens and pistil. The union of the last two petals is not 

 complete, for they have separate stalks, nor is it very close, 

 as they can readily be separated. Petals, like sepals, may be 

 spreading or reflexed, and when they are clawed the limb may 

 be bent sharply on the claw. Thus, in the wallflower there are 

 four equal petals, diagonal in position, and with long claws. 

 The limbs spread abruptly out transversely to the claws, and the 

 corolla is strikingly cross-shaped in consequence, for which reason 

 it is termed cruciferous. 



Some of the most remarkable forms of. irregular corolla are 

 found in orchids, especially tropical ones. Perhaps the com- 

 monest British species is the early purple orchis (Orchis mascida), 

 which flowers from April to June. There are here three petaloid 

 sepals, an upper one, arching over the central structures, and 

 two spreading or reflexed lateral ones. Alternating with these 

 are three other purple flower leaves, two smaller upper petals, 

 arching like the upper sepal, and a much larger three-lobed one, 

 the lahellum. The central lobe of this last is regarded as the 

 lower petal, and the two side lobes as iietaloicl stamens fused with 

 it. These conclusions are based upon comparison with allied but 

 less modified plants and the structure of the parts. Details would 



