128 SOUTH AFRICAN FLOWERING PLANTS. 



point be thrust down in imitation of an insect, the 

 flower explodes. This is caused by the stamens, 

 which lay concealed horizontally within the keel, 

 suddenly rising upwards and assuming a curyed 

 position, at the same time, it may be supposed, dust- 

 ing the bee with poUen. A similar explosion takes 

 place in some of the Polyg'ala family. 



Fig. i,<J.—£rjihr'nj. canra. L Flower. IT. Diagram: *, standard; », wings; 

 fr, ke«l ; c, calyx ; it, style. 



Cas'sia. — This is a good type of the second sub- 

 order. Fig. 51, II., is a section through the flower 

 of C. arachoi'des, and (I.) is a diagram of the same. 

 K this be compared with that of Erythri'na, it will be 

 seen that the posterior petal or standard in Erythri'na 

 oyerlaps the wings, while the keel petals are united 

 below; but the posterior petal is included within 



