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 curved 

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

 ing the bee with pollen. A similar explosion takes 

 place in some of the Polyg'ala family. 



Fig. ^,0.—£ri/lhri'na caff 'ra. I. Flower. II. Diagram 

 7i-, keel ; c, calyx ; st, stylo. 



II 



stamlard; iv, wings : 



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

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

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

 If this be compared with that of Erytliri'na, it will be 

 seen that the posterior petal or standard in Erytliri'na 

 overlaps the wings, while the keel petals are united 

 below; but the posterior petal is included tuithin 



