Tertiary Organs of Plants. 71 



the other organs while they are tender in the bud and 

 usually continues to protect the ovary while it is developing 

 into fruit. Often it forms the outside of the fruit, as in 

 apples, pears, pomegranates and squashes. The corolla is 

 a signal which shows insects where the feast of nectar is 

 spread. It also keeps unwelcome visitors out and helps 

 the welcome ones to find and easily get the nectar, while it 

 assists stamens and stigmas to deliver and receive pollen. 

 The work of the stamens is finished when the pollen which 

 they have produced has been delivered to the insect mes- 

 senger. The pistil (carpel or carpels), usually dismissing 

 the stigma soon after the pollen has been received, continues 

 its work until it becomes fruit containing ripe seeds. 

 Fruits are green in color until ripe, then they usually 

 change to a color that makes them more easily seen. The 

 pod or juicy outside of fruit usually causes the seeds to be 

 scattered often many miles from the plant which produced 

 them. Cockle-burs, bur-clover, etc., cling to animals and 

 are thus distributed. The sweet pulp of berries causes 

 them to be scattered by birds, etc. In short, an apple is 

 good that its seeds may be distributed. A cherry is red 

 that some cherry loving animal may surely find it and drop 

 its seed far from the parent tree. 



EXERCISE 40. 



Tertiary Organs or Changed Secondary Organs of 

 Plants. Rudimentary and Obsolete Organs. Your atten- 

 tion has already been called (page 38) to the fact that when 



