150 BEAN-FLOWER. [CH. XI 



it is raised like a flag, making the flower conspicuous. 

 Next come two petals, the wings or alee, standing sym- 

 metrically right and left of the median plane 1 . 



When the wings have been removed a hooded boat- 

 like structure is seen which is called the keel or carina. 

 The keel consists of two coherent petals, as is obvious 



FIG. 68. 



FLORAL DIAGRAM OF A PAPILIONACEOUS FLOWER. 

 From Le Maout and Decaisne. 



when the floral diagram (fig. 68) of a pea-flower is 

 examined. Within the five sepals (which are shaded) are 

 shown in black the parts of the corolla ; these are four 

 in number, the lower one, representing the keel, being 

 partly divided to indicate the union of two petals. The 

 point of union of the two halves of the keel comes opposite 

 the centre of the lower sepal ; in other words this sepal 

 alternates with the petals which make up the keel. In 

 fig. 69, which gives a back view of the standard, it is seen 

 that this is a single petal, since it falls between two 

 sepals : the alternation of the standard may also be seen 

 in the floral diagram. 



1 In the bean each wing is marked with a black spot. The wings 

 require some slight force to detach them since they are superficially 

 attached to the part of the corolla within, i.e. to the carina. 



