SEEDS AND SEEDLINGS 



71 



coats. There are some dicotyledonous plants that have food 

 stored outside of the embryo. Such a plant is the castor bean.^ 



Castor Bean. — A section cut vertically through the castor bean discloses 

 a white oily maes directly under the seed coats. This mass is called the 

 endosperm. If it is tested with iodine, it can be proved to contain starch; 

 oil is also present in considerable quantity Within the endosperm lies the 

 embryo, a thin, whitish 

 structure. If the embryo 

 is carefully removed from 

 the endosperm (see direc- 

 tions in preparation note, 

 page 19, Hunter and Val- 

 entine, Manual), the struc- 

 ture of the embryo can 

 easily be made out. 



Open a number of 

 soaked seeds of the fol- 

 lowing-named plants, and 

 locate, with the aid of the diagrams, the embryo and the endosperm in each: 

 four o'clock, morning glory, castor bean, maple. Make diagrams for your 

 notebook to show these facts. 



Arrangement of embryo in endosperm (Gray) ; a, morn- 

 ing glory; b, barberry; c, potato; d, four o'clock. 



A cornfield, showing staminate and pistillate flowers. 



The Corn. — The ear of corn is not a single fruit, but a large 

 number of fruits in a cluster, like, for example, a bunch of bananas. 



1 For laboiatory work on the castor bean, see Hunter and Vah^ntine, Manual, 

 page 19. 



