CHAPTER XXIV 



THE OVULE AND SEED 



1. In their young undeveloped stage seeds are 

 termed ovules. It is only after fertilization by pollen 

 that an ovule will develop into a seed, but during 

 this development very great changes in the structure 

 of the ovule take place, and it may grow to be a 

 hundred times its original size. 



The ovule arises as an outgrowth of the placenta, 

 and is at first an oval body, called the nucellus. Over 

 the nucellus there grow first one, then (in some cases) 

 another skin, the integuments, which beginning at the 

 placental basal end, grow till they cover the nucellus 

 except for a small hole at the further end. This hole 

 is called the micropyle and is really of great importance 

 to the seed (see p. 64). 



As the ovule develops into the seed, these integu- 

 ments become thicker and, when the seed is ripe, 

 form usually a firm tough covering the seed coat or 

 testa. 



At the base of the ovule there is developed a short 

 or long stalk, the funicle, connecting it with the 



