158 THE NATUEE AND WORK OF PLANTS 



b. Strip the husk from the entire fruit, and 



note its relative thickness over different 

 parts of the shell. Note also the charac- 

 ter of the fibres at the basal end. The 

 husk is derived from the wall of the 

 ovary. If the fruit were suspended on 

 its stem and were broken off suddenly, 

 which end would strike the ground first ? 

 Do you think this beneficial or not ? 

 Examine the stripped nut and note : 



c. The shape and markings of the shell. The 



three dark circular areas on the basal end 

 are the marks of the three parts or car- 

 pels of the ovary. 

 Break or cut up the nut and test 



d. The hardness of the shell. Cut with knife 



and test strength. Is it " air tight " and 

 " water tight " ? 



The husk is derived from the outer 

 wall of the ovary, and the shell from the 

 inner wall, neither being seed-coats. 



III. The seed. 



Examine the nut which has been cut, and note : 

 a. The central cavity, filled with a sweetish 



