THE FLORAL ENVELOPES. 131 



of irregularity amongst polypetalous corollas which usually 

 receives a special notice, on account of the remarkably anoma- 

 lous development of its petals, and because it is characteristic 

 of an extensive natural order of plants, viz : the papilionaceous 

 corolla, from (papilio, a butterfly,) of which the pea-flower 

 furnishes a good example. (Fig. 37.) This corolla is composed 



Fig. 37. 



of five unequal and dissimilar petals. One larger than the 

 rest, a, called the vexillum or standard, which is usually 

 folded over the other petals in aestivation ; two lateral petals, 

 b, which are designated as the alee or wings ; and two inferior 

 petals, usually completely covered by the alse, and their lower 

 margins so united as to form a single keel-like piece, called 

 the carina or keel, c. This last piece embraces the essential 

 organs, the stamens and pistils. 



The following leading forms may be distinguished amongst 

 the regular monopetalous corollas. The campanulate, or bell- 

 shapfed, as in Campanula rotundifolia, (Fig. 38, a,) which is 

 without a tube, and which enlarges gradually from the base to 

 the apex. The infundibuliform or funnel-shaped, as in the 

 Convolvulus purpureus, or morning-glory, in which the tube 

 is narrow below but widely-expanded towards the summit. 

 The hypocrateriform or salver-shaped, as in the Phlox (Fig. 

 38, 6,) where the limb spreads out at right-angles with the 



