THE LEAF. 245 



anther appear together or in succession, and, if in 

 succession, in what order. 



Observe the formations of ovules. A long time 

 before the opening of the flower, you may see a small, 

 round swelling on the placenta, which is the nucleus 

 of an ovule. Soon, around this pimple, there appears 

 a circular rim, which rises toward the summit of the 

 nucleus; and then a second rim appears, growing 

 around the first, and ending by overtaking and sur- 

 passing it. These two sacs are not entirely closed, 

 but they leave a circular opening, known to you as 

 the micropyle. Look carefully with your magnifying- 

 glass for the various parts of the ovule while it is 

 growing, and, if you have a microscope, make sec- 

 tions of it, and study its minute structure. 



