REPRODUCTION IN PLANTS 93 



104. Seed dispersal by animals. Laboratory Study No. 

 49. Study one or more of the following fruits : 



A. Burs and stickers. 



1. Cocklebur. 



a. Hold one of the fruits between yourself and the 

 light. Do the hooks all curve toward one end 

 of the fruit or in several directions ? 

 Notice the two larger projections at one end of the 

 fruit. These are the styles. Draw ( X 2) the 

 outside of one of the cockleburs, showing 

 the direction of the hooks. Label ovary, 

 hooks, two styles (large prongs at one end of 

 fruit). 



6. Rub one of the cockleburs on a rough surface of 

 your clothing and try to remove it. By what 

 means does it cling to the cloth? How is a 

 cow or other hairy animal adapted to disperse 

 this fruit? 



2. Burdock. 



a. Each burdock consists of a large number of indi- 



vidual fruits. Hold the burdock to the light. 

 In what directions do the hooks extend ? Why 

 is this an advantage in securing the distribu- 

 tion of fruits? 



b. Answer questions under 1 b above. 



3. Bidens (also called pitchforks or beggar's ticks). 



a. Hold the fruit to the light or examine it with a 



hand magnifier. In what direction do the 

 little barbs on the two prongs of the ovary 

 extend ? Why is this an advantage ? 

 Draw ( X 2) one of the bidens fruits. Label 

 ovary, prongs, barbs. 



b. Answer questions in 1 b above. 



B. Fleshy fruits. Suggested as home work. 



1. In what ways are the seeds of apples, cherries, and 

 of many other fleshy fruits protected while they 

 are ripening? 



