LABORATORY PRACTICE CHAP, xxm 



CHAPTER XXIII 



SELF-POLLINATION 



CROSS-POLLINATION seems to be the rule. Many flowers, 

 however, are so constructed that x if they fail to be cross- 

 pollinated, they are self-pollinated. But such flowers pro- 

 duce fewer and less vigorous seeds than the cross-polli- 

 nated flowers. But some flowers are especially constructed 

 for self-pollination alone. They are called cleistogamous 

 flowers. 



I. Examine the greenish flowers (produced close to the 

 ground) of the Fringed Polygala (P. paucifolia and P. 

 pofygama, of the East or any Pacific Coast species) and. 

 notice : 



1. The contrast in color between them and the upper 



flowers. 



2. The fact that fertilization takes place when the flowers 



are very small, for the ovary begins to enlarge very 

 soon. 



3. The fact that the flowers never open. 



(Dissection to demonstrate the floral organs is rather too 

 difficult for beginners.) 



4. Make sketches and notes. 



