Cross-Section oj a Cactus Blossom 



This is what is called a perfect flower that is to say one that 

 has both stamens and pistil. The stamens are grouped in a circle 

 about the pistil, as in case of the poppy, this being the typical arrange- 

 ment. The picture shows the seed case or ovary at the base of the 

 pistil. Each ovule must receive the nucleus of a pollen grain 

 or it will not develop. Where the stamens are thus clustered 

 about the pistil, cross-fertilization is usually prevented by 

 the maturing of the two sets of organs at different periods. 



